EDITORS-IN-CHIEF Marshall M Haith received his M.A and Ph.D degrees from U.C.L.A and then carried out postdoctoral work at Yale University from 1964–1966 He served as Assistant Professor and Lecturer at Harvard University from 1966–1972 and then moved to the University of Denver as Professor of Psychology, where he has conducted research on infant and children’s perception and cognition, funded by NIH, NIMH, NSF, The MacArthur Foundation, The March of Dimes, and The Grant Foundation He has been Head of the Developmental Area, Chair of Psychology, and Director of University Research at the University of Denver and is currently John Evans Professor Emeritus of Psychology and Clinical Professor of Psychiatry at the University of Colorado Health Sciences Center Dr Haith has served as consultant for Children’s Television Workshop (Sesame Street), Bilingual Children’s Television, Time-Life, and several other organizations He has received several personal awards, including University Lecturer and the John Evans Professor Award from the University of Denver, a Guggenheim Fellowship for serving as Visiting Professor at the University of Paris and University of Geneva, a NSF fellowship at the Center for Advanced Study in the Behavioral Sciences (Stanford), the G Stanley Hall Award from the American Psychological Association, a Research Scientist Award from NIH (17 years), and the Distinguished Scientific Contribution Award from the Society for Research in Child Development Janette B Benson earned graduate degrees at Clark University in Worcester, MA in 1980 and 1983 She came to the University of Denver in 1983 as an institutional postdoctoral fellow and then was awarded an individual NRSA postdoctoral fellowship She has received research funding form federal (NICHD; NSF) and private (March of Dimes, MacArthur Foundation) grants, leading initially to a research Assistant Professor position and then an Assistant Professorship in Psychology at the University of Denver in 1987, where she remains today as Associate Professor of Psychology and as Director of the undergraduate Psychology program and Area Head of the Developmental Ph.D program and Director of University Assessment Dr Benson has received various awards for her scholarship and teaching, including the 1993 United Methodist Church University Teacher Scholar of the Year and in 2000 the CASE Colorado Professor of the Year Dr Benson was selected by the American Psychological Association as the 1995–1996 Esther Katz Rosen endowed Child Policy Fellow and AAAS Congressional Science Fellow, spending a year in the United States Senate working on Child and Education Policy In 1999, Dr Benson was selected as a Carnegie Scholar and attended two summer institutes sponsored by the Carnegie Foundation program for the Advancement for the Scholarship of Teaching and Learning in Palo Alto, CA In 2001, Dr Benson was awarded a Susan and Donald Sturm Professorship for Excellence in Teaching Dr Benson has authored and co-authored numerous chapters and research articles on infant and early childhood development in addition to co-editing two books v EDITORIAL BOARD Richard Aslin is the William R Kenan Professor of Brain and Cognitive Sciences at the University of Rochester and is also the director of the Rochester Center for Brain Imaging His research has been directed to basic aspects of sensory and perceptual development in the visual and speech domains, but more recently has focused on mechanisms of statistical learning in vision and language and the underlying brain mechanisms that support it He has published over 100 journal articles and book chapters and his research has been supported by NIH, NSF, ONR, and the Packard and McDonnell Foundations In addition to service on grant review panels at NIH and NSF, he is currently the editor of the journal Infancy In 1981 he received the Boyd R McCandless award from APA (Division 7), in 1982 the Early Career award from APA (developmental), in 1988 a fellowship from the John Simon Guggenheim foundation, and in 2006 was elected to the American Academy of Arts and Sciences Warren O Eaton is Professor of Psychology at the University of Manitoba in Winnipeg, Canada, where he has spent his entire academic career He is a fellow of the Canadian Psychological Association, and has served as the editor of one of its journals, the Canadian Journal of Behavioural Science His current research interests center on child-to-child variation in developmental timing and how such variation may contribute to later outcomes Robert Newcomb Emde is Professor of Psychiatry, Emeritus, at the University of Colorado School of Medicine His research over the years has focused on early socio-emotional development, infant mental health and preventive interventions in early childhood He is currently Honorary President of the World Association of Infant Mental Health and serves on the Board of Directors of Zero To Three Hill Goldsmith is Fluno Bascom Professor and Leona Tyler Professor of Psychology at the University of Wisconsin–Madison He works closely with Wisconsin faculty in the Center for Affective Science, and he is the coordinator of the Social and Affective Processes Group at the Waisman Center on Mental Retardation and Human Development Among other honors, Goldsmith has received an National Institute of Mental Health MERIT award, a Research Career Development Award from the National Institute of Child Health and Human Development, the James Shields Memorial Award for Twin Research from the Behavior Genetics Association, and various awards from his university He is a Fellow of AAAS and a Charter Fellow of the Association for Psychological Science Goldsmith has also served the National Institutes of Health in several capacities His editorial duties have included a term as Associate Editor of one journal and membership on the editorial boards of the five most important journals in his field His administrative duties have included service as department chair at the University of Wisconsin Richard B Johnston Jr is Professor of Pediatrics and Associate Dean for Research Development at the University of Colorado School of Medicine and Associate Executive Vice President of Academic Affairs at the National Jewish Medical & Research Center He is the former President of the American Pediatric Society and former Chairman of the International Pediatric Research Foundation He is board certified in pediatrics and infectious disease He has previously acted as the Chief of Immunology in the Department of Pediatrics at Yale University School of Medicine, been the Medical Director of the March of Dimes Birth Defects Foundation, Physician-in-Chief at the Children’s Hospital of Philadelphia and Chair of the Department of Pediatrics at the University Pennsylvania School of Medicine He is editor of ‘‘Current Opinion in Pediatrics’’ and has formerly served on the editorial board for a host of journals in pediatrics and infectious disease He has published over 80 scientific articles and reviews and has been cited over 200 times for his articles on tissue injury in inflammation, granulomatous disease, and his New England Journal of Medicine article on immunology, monocytes, and macrophages vii viii Editorial board Jerome Kagan is a Daniel and Amy Starch Professor of Psychology at Harvard University Dr Kagan has won numerous awards, including the Hofheimer Prize of the American Psychiatric Association and the G Stanley Hall Award of the American Psychological Association He has served on numerous committees of the National Academy of Sciences, The National Institute of Mental Health, the President’s Science Advisory Committee and the Social Science Research Council Dr Kagan is on the editorial board of the journals Child Development and Developmental Psychology, and is active in numerous professional organizations Dr Kagan’s many writings include Understanding Children: Behavior, Motives, and Thought, Growth of the Child, The Second Year: The Emergence of Self-Awareness, and a number of cross-cultural studies of child development He has also coauthored a widely used introductory psychology text Professor Kagan’s research, on the cognitive and emotional development of a child during the first decade of life, focuses on the origins of temperament He has tracked the development of inhibited and uninhibited children from infancy to adolescence Kagan’s research indicates that shyness and other temperamental differences in adults and children have both environmental and genetic influences Rachel Keen (formerly Rachel Keen Clifton) is a professor at the University of Virginia Her research expertise is in perceptual-motor and cognitive development in infants She held a Research Scientist Award from the National Institute of Mental Health from 1981 to 2001, and currently has a MERIT award from the National Institute of Child Health and Human Development She has served as Associate Editor of Child Development (1977–1979), Psychophysiology (1972–1975), and as Editor of SRCD Monographs (1993–1999) She was President of the International Society on Infant Studies from 1998–2000 She received the Distinguished Scientific Contribution Award from the Society for Research in Child Development in 2005 and was elected to the American Academy of Arts and Science in 2006 Ellen M Markman is the Lewis M Terman Professor of Psychology at Stanford University Professor Markman was chair of the Department of Psychology from 1994–1997 and served as Cognizant Dean for the Social Sciences from 1998–2000 In 2003 she was elected to the American Academy of Arts and Sciences and in 2004 she was awarded the American Psychological Association’s Mentoring Award Professor Markman’s research has covered a range of issues in cognitive development including work on comprehension monitoring, logical reasoning and early theory of mind development Much of her work has addressed questions of the relationship between language and thought in children focusing on categorization, inductive reasoning, and word learning Yuko Munakata is Professor of Psychology at the University of Colorado, Boulder Her research investigates the origins of knowledge and mechanisms of change, through a combination of behavioral, computational, and neuroscientific methods She has advanced these issues and the use of converging methods through her scholarly articles and chapters, as well as through her books, special journal issues, and conferences She is a recipient of the Boyd McCandless Award from the American Psychological Association, and was an Associate Editor of Psychological Review, the field’s premier theoretical journal Arnold J Sameroff, is Professor of Psychology at the University of Michigan where he is also Director of the Development and Mental Health Research Program His primary research interests are in understanding how family and community factors impact the development of children, especially those at risk for mental illness or educational failure He has published 10 books and over 150 research articles including the Handbook of Developmental Psychopathology, The Five to Seven Year Shift: The Age of Reason and Responsibility, and the forthcoming Transactional Processes in Development Among his honors are the Distinguished Scientific Contributions Award from the Society for Research in Child Development and the G Stanley Hall Award from the American Psychological Association Currently he is President of the Society for Research in Child Development and serves on the executive Committee of the International Society for the Study of Behavioral Development FOREWORD This is an impressive collection of what we have learned about infant and child behavior by the researchers who have contributed to this knowledge Research on infant development has dramatically changed our perceptions of the infant and young child This wonderful resource brings together like a mosaic all that we have learned about the infant and child’s behavior In the 1950s, it was believed that newborn babies couldn’t see or hear Infants were seen as lumps of clay that were molded by their experience with parents, and as a result, parents took all the credit or blame for how their offspring turned out Now we know differently The infant contributes to the process of attaching to his/her parents, toward shaping their image of him, toward shaping the family as a system, and toward shaping the culture around him Even before birth, the fetus is influenced by the intrauterine environment as well as genetics His behavior at birth shapes the parent’s nurturing to him, from which nature and nurture interact in complex ways to shape the child Geneticists are now challenged to couch their findings in ways that acknowledge the complexity of the interrelation between nature and nurture The cognitivists, inheritors of Piaget, must now recognize that cognitive development is encased in emotional development, and fueled by passionately attached parents As we move into the era of brain research, the map of infant and child behavior laid out in these volumes will challenge researchers to better understand the brain, as the basis for the complex behaviors documented here No more a lump of clay, we now recognize the child as a major contributor to his own brain’s development This wonderful reference will be a valuable resource for all of those interested in child development, be they students, researchers, clinicians, or passionate parents T Berry Brazelton, M.D Professor of Pediatrics, Emeritus Harvard Medical School Creator, Neonatal Behavioral Assessment Scale (NBAS) Founder, Brazelton Touchpoints Center ix PREFACE Encyclopedias are wonderful resources Where else can you find, in one place, coverage of such a broad range of topics, each pursued in depth, for a particular field such as human development in the first three years of life? Textbooks have their place but only whet one’s appetite for particular topics for the serious reader Journal articles are the lifeblood of science, but are aimed only to researchers in specialized fields and often only address one aspect of an issue Encyclopedias fill the gap In this encyclopedia readers will find overviews and summaries of current knowledge about early human development from almost every perspective imaginable For much of human history, interest in early development was the province of pedagogy, medicine, and philosophy Times have changed Our culling of potential topics for inclusion in this work from textbooks, journals, specialty books, and other sources brought home the realization that early human development is now of central interest for a broad array of the social and biological sciences, medicine, and even the humanities Although the ‘center of gravity’ of these volumes is psychology and its disciplines (sensation, perception, action, cognition, language, personality, social, clinical), the fields of embryology, immunology, genetics, psychiatry, anthropology, kinesiology, pediatrics, nutrition, education, neuroscience, toxicology and health science also have their say as well as the disciplines of parenting, art, music, philosophy, public policy, and more Quality was a key focus for us and the publisher in our attempts to bring forth the authoritative work in the field We started with an Editorial Advisory Board consisting of major contributors to the field of human development – editors of major journals, presidents of our professional societies, authors of highly visible books and journal articles The Board nominated experts in topic areas, many of them pioneers and leaders in their fields, whom we were successful in recruiting partly as a consequence of Board members’ reputations for leadership and excellence The result is articles of exceptional quality, written to be accessible to a broad readership, that are current, imaginative and highly readable Interest in and opinion about early human development is woven through human history One can find pronouncements about the import of breast feeding (usually made by men), for example, at least as far back as the Greek and Roman eras, repeated through the ages to the current day Even earlier, the Bible provided advice about nutrition during pregnancy and rearing practices But the science of human development can be traced back little more than 100 years, and one can not help but be impressed by the methodologies and technology that are documented in these volumes for learning about infants and toddlers – including methods for studying the role of genetics, the growth of the brain, what infants know about their world, and much more Scientific advances lean heavily on methods and technology, and few areas have matched the growth of knowledge about human development over the last few decades The reader will be introduced not only to current knowledge in this field but also to how that knowledge is acquired and the promise of these methods and technology for future discoveries CONTENTS Several strands run through this work Of course, the nature-nurture debate is one, but no one seriously stands at one or the other end of this controversy any more Although advances in genetics and behavior genetics have been breathtaking, even the genetics work has documented the role of environment in development and, as Brazelton notes in his foreword, researchers acknowledge that experience can change the wiring of the brain as well as how actively the genes are expressed There is increasing appreciation that the child develops in a transactional context, with the child’s effect on the parents and others playing no small role in his or her own development There has been increasing interest in brain development, partly fostered by the decade of the Brain in the 1990s, as we have learned more about the role of early experience in shaping the brain and consequently, personality, emotion, and xi xii Preface intelligence The ‘brainy baby’ movement has rightly aroused interest in infants’ surprising capabilities, but the full picture of how abilities develop is being fleshed out as researchers learn as much about what infants can not do, as they learn about what infants can Parents wait for verifiable information about how advances may promote effective parenting An increasing appreciation that development begins in the womb rather than at birth has taken place both in the fields of psychology and medicine Prenatal and newborn screening tools are now available that identify infants at genetic or developmental risk In some cases remedial steps can be taken to foster optimal development; in others ethical issues may be involved when it is discovered that a fetus will face life challenges if brought to term These advances raise issues that currently divide much of public opinion Technological progress in the field of human development, as in other domains, sometimes makes options available that create as much dilemma as opportunity As globalization increases and with more access to electronic communication, we become ever more aware of circumstances around the world that affect early human development and the fate of parents We encouraged authors to include international information wherever possible Discussion of international trends in such areas as infant mortality, disease, nutrition, obesity, and health care are no less than riveting and often heartbreaking There is so much more to The central focus of the articles is on typical development However, considerable attention is also paid to psychological and medical pathology in our attempt to provide readers with a complete picture of the state of knowledge about the field We also asked authors to tell a complete story in their articles, assuming that readers will come to this work with a particular topic in mind, rather than reading the Encyclopedia whole or many articles at one time As a result, there is some overlap between articles at the edges; one can think of partly overlapping circles of content, which was a design principle inasmuch as nature does not neatly carve topics in human development into discrete slices for our convenience At the end of each article, readers will find suggestions for further readings that will permit them to take off in one neighboring direction or another, as well as web sites where they can garner additional information of interest AUDIENCE Articles have been prepared for a broad readership, including advanced undergraduates, graduate students, professionals in allied fields, parents, and even researchers for their own disciplines We plan to use several of these articles as readings for our own seminars A project of this scale involves many actors We are very appreciative for the advice and review efforts of members of the Editorial Advisory Board as well as the efforts of our authors to abide by the guidelines that we set out for them Nikki Levy, the publisher at Elsevier for this work, has been a constant source of wise advice, consolation and balance Her vision and encouragement made this project possible Barbara Makinster, also from Elsevier, provided many valuable suggestions for us Finally, the Production team in England played a central role in communicating with authors and helping to keep the records straight It is difficult to communicate all the complexities of a project this vast; let us just say that we are thankful for the resource base that Elsevier provided Finally, we thank our families and colleagues for their patience over the past few years, and we promise to ban the words ‘‘encyclopedia project’’ from our vocabulary, for at least a while Marshall M Haith and Janette B Benson Department of Psychology, University of Denver Denver, Colorado, USA PERMISSION ACKNOWLEDGMENTS The following material is reproduced with kind permission of Oxford University Press Ltd Figure of Self-Regulatory Processes http://www.oup.co.uk/ The following material is reproduced with kind permission of AAAS Figure of Maternal Age and Pregnancy Figures 1a, 1b and 1c of Perception and Action http://www.sciencemag.org The following material is reproduced with kind permission of Nature Publishing Group Figure of Self-Regulatory Processes http://www.nature.com/nature The following material is reproduced with kind permission of Taylor & Francis Ltd Figure 4b of Visual Perception http://www.tandf co.uk/journals R Reasoning in Early Development E K Scholnick, University of Maryland, College Park, MD, USA ã 2008 Elsevier Inc All rights reserved Glossary Analogical reasoning – Based on the discovery that two systems have some similar internal relations, inferences are made that there additional ways the systems correspond to one another Basic level – The most accessible level of categorization in a hierarchy because the instances in the class are fairly similar but also are fairly distinct from members of other categories In the hierarchy of poodles, dogs, and canines, ‘dogs’ is the basic category Deduction – Drawing the implications of a sentence according to a set of laws Essentialism – The belief that for each category of things found in nature, whether they are animals, vegetables, or minerals, there is an underlying invisible essence that causes things to be the way they are Induction – Reasoning from knowledge of one particular to another particular or from a particular fact to a general law Modus ponens – A form of conditional reasoning which permits a deduction from an ifstatement ‘If p, then q’ When p is true, then q must also be true Modus tollens – A form of conditional reasoning which permits a deduction from an if-statement ‘If p, then q’ If q is false, then p must be false, too Natural kinds – Classes of entities occurring in nature such as animals, plants, and minerals Instances of a class seem to share a common essence (see essentialism) Pragmatic schema – A set of rules for social interactions, such as permissions and obligations Introduction Why does the topic of reasoning belong in a volume devoted to infants and preschoolers? Should we expect toddlers to exercise the rules of thought that enable the derivation of new information from earlier material? Suppose the child is promised, ‘‘If it is sunny, we will go to the zoo tomorrow.’’ When the child wakes up the next day and learns the zoo trip is canceled, can we expect her to rush to the window to see the rain? If the toddler is told that he needs exercise to make him strong, will he infer that his dog does, too? Clearly having strong reasoning skills would be advantageous to young children in their quest to grasp the intricate patterns that shape our universe and our daily lives The child would not have to repeat the same lesson every time a new event or object appeared The early emergence of reasoning would explain how easily children learn to name objects, embark upon a vocabulary spurt, figure out how to combine words, and construct a grammar But the realm of deduction has been the exclusive purview of philosophers and geometers, and induction and analogy are the tools of scientists and inventors Are there really practicing Aristotles in the nursery? If so, what enables them to it? Maybe they are simply practicing ‘toy’ versions of reasoning with miniature tools that will grow in size, power, and complexity just as their body grows throughout childhood The study of early reasoning is fascinating because it tracks the origins of processes that uniquely characterize our species These origins have been controversial because the cognitive revolution in psychology was accompanied by a second revolution in developmental psychology which eradicated the barriers between mature and infant thought Additionally computational models have redefined the nature of the processes by which inductions, deductions, and analogies are accomplished and the methods by which they are studied The debates about whether, when, and how youngsters reason are intimately linked to Reasoning in Early Development the process of taking reasoning from the nursery into the laboratory and using laboratory data to model thought A Framework for Understanding Issues in the Development of Reasoning The deduction about the zoo trip was triggered by a sentence with a subordinate if-clause followed by a main clause, or in formal logic, an initial premise with antecedent (if p) and consequent (then q) clauses A second premise provided new information that denied the consequent (not q, no trip) Conditional logic dictates the conclusion about the status of the antecedent precondition (not p, no sun) ‘If ’ often signals that the original premise is hypothetical Who knows tomorrow’s weather? The sentence describes a familiar event The toddler has visited the zoo under diverse weather conditions and knows that thunderstorms ruin excursions Pragmatically, the parent has promised an excursion under certain preconditions In daily life, interpretations of conditional premises draw upon knowledge of logic, syntax, social interactions, and events, and the child who is developing competence in reasoning is simultaneously gaining social and linguistic competencies which may support reasoning There are multiple redundant cues and multiple redundant processes by which the information can be extended But the scientific study of psychological processes is analytic and focuses on single processes at their simplest level This reductionist approach presents barriers to the study of children’s reasoning Each facet of reasoning, its syntax, semantics, pragmatics, and logical form, facilitates reasoning As each is removed, reasoning becomes harder and more inaccurate and young children seem less competent Moreover, our models of reasoning and its origins become impoverished because they not encompass the multiple inroads available to children depending on the circumstances and skills of the child The definition of reasoning is also elusive Four new pieces of information could follow the premise, ‘‘If it is sunny, we will go to the zoo.’’ Two focus on the antecedent if-clause and either affirm the precondition of a sunny day (modus ponens) or deny it, citing rain, and then leave the reasoner to decide whether there will be a zoo trip Two others focus on the consequent, either affirming that the zoo trip occurred, or as in the modus tollens example that canceled the trip, denying the consequent clause, leaving the reasoner to infer the weather conditions Modus ponens reasoning is accessible to toddlers but college sophomores studying logic err in the inferences they draw from affirming the consequent or denying the antecedent because the inference is indeterminate The ifpremise states what happens when its precondition is satisfied, but says nothing about what happens when it is not satisfied The abysmal performance of adults on problems with indeterminate answers led to claims that some or all of conditional logic falls outside the province of mature reasoners, much less children The more encompassing the definition of reason, the more likely complex processing will be required to exhibit the skill, and competence will appear late in development There are also levels of understanding of reasoning, and where the bar is set may determine the age of emergence and the level of competence attributed to the reasoner Children may know the agenda for a zoo trip on a sunny day Do children also know that canceling the excursion on a sunny day would make their mother a liar? Forms of inference and their ramifications, like falsification strategies, may not emerge simultaneously Just as President Clinton once tried to evade his questioners by noting that it depends on what the meaning of ‘is’ is, analyses of reasoning depend on what the meaning of reasoning is Debates about the emergence of reasoning fall into three camps The first camp inspired the question, ‘‘What’s the topic of reasoning doing in this volume?’’ Reasoning is a higher order skill best studied with abstract materials, and embedded in two interlocking systems, of mutually entailing rules and conscious awareness of their conditions of operation The rules are idealizations that most individuals rarely attain Only logicians and scientists reason with any facility The rules exemplify what children can aspire to master The study of logic in childhood is either an oxymoron or a search for the roots The second, opposing view posits scientists in the crib, born with either powerful reasoning devices that undergird learning or powerful belief systems about domains like biology or social behavior that support reasoning The early emergence of reasoning demonstrates the power of our evolutionary endowment to prepare children to adapt to the world The third view is developmental There are pronounced changes in children’s reasoning skills This perspective encompasses lively debates about starting points, developmental mechanisms, benchmarks of change, and final destinations Some researchers ground early reasoning in dumb mechanisms like attention, perception, and association that become smarter and more abstract Alternatively the initial theory of the world that undergirds reasoning may undergo radical changes The choice of theory and its characterization of young children reflect prior choices of the definition of reasoning and the contexts in which it is studied This article provides a survey of 2–5-year-old’s inductive, analogical, and deductive inference performance that bears on these debates Induction Induction extends information known about one particular to another or from a particular to the general Scientists Visual Perception photoreceptors, and their associated percepts of color, are functional This question of chromatic discrimination is a subtle one and requires exquisite control over the visual displays because any chromatic stimulus has at least two properties: color (wavelength) and brightness (intensity) Consider an infant who has only a single class of photoreceptors and is presented with a checkerboard made up of red and green checks If the brightness of the red and green checks is not perfectly matched (by varying the physical property of luminance), then the infant may see the checkerboard as a set of shades of gray and not as red/ green To overcome this so-called brightness confound, Davida Teller and her colleagues used the FPL technique to present a single bar of one color on a background of another color (see Figure 3) The bar appeared on the right or left side of the display from trial to trial, and the task was to determine whether the infant looked reliably at the side of the display on which the bar was presented To eliminate the brightness confound, the luminance of the bar was varied over a wide range with respect to the fixed luminance of the background By using small steps in luminance, it was assured that one of these displays contained a brightness match between the bar and the background The logic of this task is that, if the infant had only one class of photoreceptors (and therefore perceived the bar and background as shades of gray), then when the luminance was perfectly matched the bar would (a) 399 be invisible In contrast, if the infant had at least two classes of photoreceptors, then no matter what the luminance match of the bar and background, the bar would still be visible This technique showed conclusively that 2-month-olds could discriminate red from green, thereby demonstrating that two classes of photoreceptors were functional at this age Subsequent studies addressed more subtle questions and showed that chromatic discrimination is not adultlike until at least months of age Whereas even newborns can discriminate red from white light (the latter contains all wavelengths), the class of photoreceptors sensitive to blue light are not functional until months of age, at which point infants, like adults, are characterized as trichromats (having three functional classes of cones) Prior to months, infants have much more difficulty discriminating small differences in color, and these deficiencies are largely the result of the immaturity of the photoreceptors (see previous section on retinal anatomy), which renders their signals noisy Because color perception requires a computation of the difference in outputs from pools of two or three classes of photoreceptors, these noisy signals reduce chromatic discriminability Color constancy, the ability of infants to perceive the correct color despite variations in lighting (e.g., ignoring the reddish tint at sunset), emerges between and months of age Infants were habituated to a colored surface that was illuminated with one of two light sources (e.g., slightly bluish) and then tested with a novel colored surface under that same lighting conditions or the same colored surface under novel lighting conditions (e.g., slightly reddish) Infants younger than months of age treated both test displays as novel, whereas older infants treated the same colored surface with different illuminations as the same, thereby showing evidence of color constancy Similar research has recently been conducted on lightness constancy: the ability to perceive the same black-white object as having a stable brightness (shade of gray) despite changes in the intensity of the light source that illuminates it Again, evidence of lightness constancy was not present until months of age Motion (b) Figure The appearance of an FPL display used to measure color discrimination when the infant (a) has color vision or (b) is colorblind In both cases, the small bar differs in luminance from the background Moving stimuli are more effective at capturing infants’ attention than stationary stimuli This natural bias to attend to moving stimuli has been used in preferential looking studies to estimate motion thresholds: the minimum stimulus speed required to discriminate a moving from an otherwise identical stationary stimulus Motion thresholds improve dramatically in early infancy despite nearly adult-like temporal sensitivity at birth (e.g., ability to detect a flickering light), suggesting that these improvements in motion sensitivity rely critically on improvements in spatial resolution It is clear, however, that by weeks of 400 Visual Perception age infants detect a moving set of stripes based on their speed and not their local flicker This conclusion was demonstrated by pairing a moving set of stripes with an identical but stationary set of stripes in an FPL experiment On half of the trials the stripes were doubled in width Thus, if both narrow and thick stripes moved at the same speed, they would create different flicker rates Results showed that speed and not flicker rate best predicted infants’ thresholds for preferring the moving stripes over the stationary stripes Discrimination of different directions of motion is the definitive test of a motion mechanism because the responses of single neurons in many parts of the brain have a preferred direction of stimulus motion The FPL technique has been used with two different arrays of randomly arranged dots that move in coherent directions on the two sides of the display On one side, all the dots move in a single direction, and on the other side some of the dots move leftward and others move rightward (see Figure 4(a)) If infants can discriminate these different directions of motion, then they should prefer the side of the display that contains a motion-contrast over the side that contains a uniform (a) (b) Figure Two types of random-dot displays for measuring (a) direction-discrimination, and (b) optic flow (a) Reproduced from Wattam-Bell J (1992) The development of maximum displacement limits for discrimination of motion direction in infancy Vision Research 32(4): 621–630, with permission from Elsevier (b) Reproduced from Gilmore RO and Rettke HR (2003) Four-month-olds’ discrimination of optic flow patterns depicting different directions of observer motion Infancy 4(2): 177–200, with permission from Taylor and Francis direction of dot-motion However, FPL studies have failed to demonstrate infants’ discrimination of opposite directions of stimulus motion until months of age Notice that this use of the FPL technique is different from a ‘detection’ task (as in visual acuity) because now both sides of the display contain highly visible elements When the FPL technique is used to assess stimulus ‘discrimination’, evidence of a significant preference allows for the conclusion that infants can discriminate the difference between the two stimuli However, the absence of a significant preference is ambiguous because the two stimuli may be discriminable but fail to elicit a clear preference in looking behavior In an attempt to remedy this problem of equal stimulus preference, the habituation technique was developed to induce preferences that were not spontaneously present Fantz noted in his early studies of preferential looking that when the same two stimuli were presented sideby-side, fixation durations declined across repeated trials This decrement in looking duration is called habituation and indicates that the infant has processed and retained some information about the stimulus across time Subsequent elaborations on the use of habituation as a measure of visual discrimination have resulted in an ‘industry standard’ that consists of two phases: habituation and test During habituation, a single visual stimulus is presented and an observer records how long the infant sustains fixation (interrupted by no more than s of distraction) to that stimulus on a given trial Identical trials are repeated, tallying fixation duration until there is a preset decrement (typically 50%) from the initial level of looking on the first several trials When this criterion of habituation has been met, the infant enters a test phase in which the same habituation stimulus and a novel stimulus are presented on alternating trials Continued low levels of looking to the habituation stimulus and significant increases (recovery) of looking to the novel stimulus are taken as evidence of discriminating the habituation (familiar) from the novel stimulus The habituation technique has been used to assess direction discrimination of sets of random-dot displays Infants viewed a coherent direction of dot-motion that was changed (e.g., from right to left ) after the habituation criterion was met As in the FPL paradigm, infants failed to discriminate a change to the opposite direction of motion until 8–9 weeks of age This relatively late onset of motion discrimination is surprising because even newborns show directionally appropriate eye movements to stripemotion during OKN In addition, if infants view a large field of coherently moving dots in a FPL design, observers are quite accurate at judging in which the direction the dots are moving based on the infant’s eye movements, even if full-blown OKN is not present Moreover, this task shows no apparent changes in performance across the first Visual Perception months of life Thus, it has been concluded that cortical mechanisms of motion processing are not functional until the third postnatal month, whereas brainstem mechanisms of motion processing involved in eye-movement control are functional at birth Additional support for this dual-pathway theory of motion processing comes from studies of OKN in infants who have not yet attained functional binocular vision (under months of age; see section on Depth and Binocular Rivalry) Binocular vision is clearly mediated by the cortex (not by brainstem mechanisms) and young infants show an asymmetry in the direction of OKN when one eye is patched (temporalward stripe motion is ineffective in eliciting monocular OKN in newborns) This asymmetry disappears by months of age, presumably because cortical mechanisms override the brainstem mechanisms that initially control OKN In addition, this nasal-temporal OKN asymmetry in young infants is mirrored in the VEP when assessed under monocular viewing conditions That is, the minimum contrast required to elicit a VEP to a set of stripes moving nasally is less than the minimum contrast to a set of stripes moving temporally Motion stimuli in the natural environment not consist entirely of uniform directions, but often involve complex patterns of motion directions For example, when an observer moves through space in a forward direction, pattern elements projected on the retina move in a radial configuration, with the direction of heading creating a point in the retinal array that is stationary (see Figure 4(b)) This pattern of motion is called optic flow and is extremely useful for spatial orientation during locomotion However, to use this optic flow information for guiding locomotion, infants must be able to discriminate different aspects of radial motion, such as the direction of heading Recent FPL and habituation studies confirm that even 4-month-olds are very poor at discriminating changes in heading from optic flow displays Thus, it has been proposed that until infants begin self-produced locomotion as they begin to crawl, they are relatively inattentive to these useful visual cues Orientation and Vernier Acuity Another fundamental property of neurons in the visual cortex is orientation sensitivity, and this property is present in rudimentary form in newborn cats and monkeys Human newborns are also sensitive to orientation, but only for gross differences Studies have shown that when newborns are habituated to a set of horizontal or vertical stripes, they show increases in fixation to a change to the other orientation Similar results have been obtained with a shift from one diagonal (45 tilt) to another diagonal (135 tilt) The VEP technique provides converging 401 evidence for orientation discrimination In this design a set of stripes of a particular orientation is flashed at a high rate (e.g., every 0.5 s) and at intermittent intervals (e.g., every 5–8 flashes) the orientation of the stripes is altered By examining the electrical potentials that are elicited at these shifts in stripe orientation, one can determine if the shift was discriminated, and results indicated that they were at very early ages Although the foregoing results show that a rudimentary orientation mechanism is present at birth, a VEP masking technique has provided a more fine-grained measure of orientation sensitivity Two sets of stripes with slightly different orientations were superimposed, and these sets of stripes were flickered at different rates In adults, orientations that are similar reduce the amplitude of the VEP signal, whereas highly discrepant orientations (e.g., horizontal and vertical) have no effect on the VEP signal Surprisingly, infants under months of age showed no evidence of this orientation masking effect even for highly similar orientations, suggesting that the rudimentary orientation discrimination present in newborns improves substantially over the next several months An even more precise measure of orientation discrimination is assessed by so-called vernier or displacement acuity displays in which observers must discriminate the spatial offset of two line segments In adults, vernier acuity is far superior to grating acuity; for example, adults can detect a stripe-width in a grating of of arc (1/60 of a deg), but they can detect the offset of two abutting line segments of only 10 s of arc (1/360 of a degree) Because the smallest receptive field in the center of the retina subtends only 20–30 s of arc, the term hyperacuity has been coined to describe the exquisite resolution on vernier tasks In infants prior to months of age, vernier acuity is poorer than grating acuity, but it improves at a more rapid rate and surpasses grating acuity This developmental difference in the relation between vernier and grating acuity has been documented using both preferential looking and VEPs One potential cue for solving a vernier acuity task is the slight orientation difference between the two line segments Thus, the protracted development of orientation sensitivity may account for the developental crossover in the relation between vernier and grating acuity The period of improvement in vernier acuity extends well into middle childhood There are several potential reasons why vernier acuity and orientation discrimination may be poor in infancy One reason is the poor resolution of the photoreceptor mosaic which limits spatial resolution in general (as in grating acuity) Another is the elaboration of cortical mechanisms sensitive to fine spatial offsets and to contour orientation A third reason is intrinsic noise in neural mechanisms used to make these two types of discrimination Studies using FPL and VEP have been conducted 402 Visual Perception with infants to assess the magnitude of this intrinsic noise The logic of these studies is that adding physical noise to the stimulus display should have no negative consequences for infant performance as long as the added noise is less than the internal (intrinsic) noise However, once the external noise exceeds the internal noise, performance should degrade with increasing external noise This technique showed that infants indeed have higher levels of intrinsic noise than adults, and the decreasing estimate of intrinsic noise predicted the developmental improvements in vernier acuity (a) Depth and Binocular Rivalry The relative distance (depth) of objects can be appreciated using three different sources of information: motion, retinal disparity, and pictorial cues (this last cue is discussed in the chapter by Arterberry) A rapidly approaching (looming) stimulus elicits a blink response in 1-month-olds, but only if the projected motion (an expansion pattern) is symmetrical, corresponding to a path that would collide with the infant’s face This finding is interesting in light of the rather poor sensitivity of infants to patterns of optic flow that not correspond to a looming stimulus Another cue to depth is motion parallax, which is created whenever an object moves with respect to an observer (or an observer moves with respect to an object) The speed with which the image of the object moves across the retina is proportional to viewing distance (more rapid image speed for near than for far objects) Studies have shown that 3-month-olds are quite sensitive to small differences in object distance defined solely by motion parallax Interestingly, these motion-defined cues entail much slower speeds than estimated from studies of motion thresholds using nondepth stimuli, suggesting that motion and depth cues are intricately related in the developing visual system Importantly, sensitivity to depth from motion (in looming and motion parallax displays) is present in very early infancy and does not require the use of both eyes Although motion-defined depth is finely tuned in adults, purely binocular information has much greater resolution than motion information Binocular disparity refers to the subtle differences in the images projected to the two retinas from an object at near (less than m) viewing distances (see Figure 5) Stereopsis refers to the appreciation of depth based solely on binocular disparity FPL and VEP studies using stereograms have demonstrated that sensitivity to binocular disparity does not emerge until 3–4 months after birth This delayed onset, as in the case of direction discrimination for motion stimuli, does not appear to be a problem of spatial resolution or attention Rather, it appears that the cortical mechanism that supports stereopsis is not functional until several months after birth Moreover, the smallest binocular disparity that is just discriminable by infants, called stereoacuity, improves very (b) Figure Two types of displays used to measure sensitivity to retinal disparity as the infant’s eyes are covered by one red and one green filter: (a) line stereogram, and (b) random-element stereogram The small box in the lower-right corner of each display represents a top-down view of how the elements in the display are perceived in depth to a normal adult rapidly between and months of age, progressing from no sensitivity to nearly adult values (less than of arc) in this age range During this same age range, infants become sensitive to binocular rivalry: the perceptual conflict induced by presenting grossly different images to the two retinas (e.g., horizontal stripes in one eye and vertical stripes in the other) Binocular rivalry occurs when the discrepant retinal images cannot be fused into a single percept Prior to months of age, infants appear to have a much greater tolerance for fusing discrepant images than adults, perhaps because of their poor acuity and contrast sensitivity However, recent evidence calls into question this conclusion, and suggests that binocular rivalry may be present prior to the onset of stereopsis One hypothesis that may accommodate both of these findings is that young infants spontaneously alternate fixation between the two eyes, thereby failing to experience binocular rivalry until the two eyes are precisely aligned on a single object of attention In adults, failure to align both foveas onto a stimulus typically leads to binocular rivalry and prevents stereopsis Some individuals, including some infants, have an ocular misalignment (strabismus) that eliminates fusion and stereopsis If uncorrected in infancy, this misalignment can result in a permanent loss of the capacity for stereopsis, even if the eyes are surgically realigned in childhood Thus, there is a sensitive period during which a normally Visual Perception developing neural mechanism for stereopsis, present by months of age, can be permanently disabled by subsequent abnormal binocular experience (strabismus) As discussed earlier (in the Motion section), infants younger than months of age show an asymmetry in their monocular OKN (a nasal-temporal bias) that disappears once stereopsis emerges Infants with strabismus who have not yet had their eye alignment corrected surgically, continue to show this OKN asymmetry This suggests, again, that there is a tight linkage between motion and depth mechanisms during development Synethesia: Separate Pathways? An unusual clinical syndrome that afflicts a very small percentage of the adult population is synethesia: the mixing of percepts between the sensory modalities For example, some synesthetes perceive each letter of the alphabet as having a specific color, despite the fact that on the printed page all the letters are black Other synesthetes experience specific tastes or smells when certain sounds are presented Although one theory of synesthesia suggests that these cross-domain experiences were created by past associations, that seems unlikely in many cases because there was no consistent linkage between the specific domains in early childhood An alternative hypothesis is that synesthesia is the normal state of the infant brain, which is then replaced by domain-specific pathways as ‘extra’ connections are gradually pruned away by early experience Research with animals has shown that developmental pathways are much more interconnected in infants than in adults, and perhaps in some individuals these early pathways, although based on false correlations between modalities, are nevertheless retained Developmental Mechanisms: Nature and Nurture The development of mature visual perception during early infancy is influenced by both maturational and experiential mechanisms Maturational factors include neural developments, such as the migration of photoreceptors (increasing the packing density of cones in the fovea) Another is the increasing selectivity of receptive fields in the visual cortex One result of such maturational factors is a reduction in the intrinsic neural noise that limits stimulus detection and discrimination Experiential factors include periods of susceptibility to altered visual input Although the range of visual inputs sufficient to enable ‘normal’ visual development is quite broad, visual deprivation (e.g., 403 cataracts or strabismus) during a sensitive period can lead to permanent deficits in visual development Much has been discovered about the basic sensitivities of the visual system in young infants over the past 40 years However, there is still much to be learned about how these basic abilities are converted into higher-level percepts and integrated with motor systems The classic view that we begin life by perceiving elementary sensations (the proximal information impinging on the retina) and only later, by a protracted process of learning, construct internal representations of the external world (the distal information that we experience), has largely been shown to be incorrect Newborns are already tuned to the distal properties of the environment (e.g., they blink to looming displays, perceive oriented contours, and discriminate colors) However, young infants have much to learn from their visual world, and their abilities increase substantially during the first postnatal year These improvements in basic visual sensitivities set the stage for the higher-level perception of objects and events that is acquired by sophisticated learning mechanisms See also: Attention; Artistic Development; Brain Development; Habituation and Novelty; Nature vs Nurture; Perception and Action; Perceptual Development; Vision Disorders and Visual Impairment Suggested Readings Atkinson J (2000) The Developing Visual Brain New York: Oxford University Press Daw NW (1995) Visual Development New York: Plenum Press Gilmore RO and Rettke HR (2003) Four-month-olds’ discrimination of optic flow patterns depicting different directions of observer motion Infancy 4(2): 177–200 Kellman PJ and Arterberry ME (1998) The Cradle of Knowledge: Development of Perception in Infancy Cambridge, MA: MIT Press Kellman PJ and Arterberry ME (2006) Infant visual perception In: Damon W, Kuhn D, and Siegler RS (eds.) Handbook of Child Psychology: Cognition, Perception, and Language, vol 2, pp 109–160 New York: Wiley Simons K (1993) Early Visual Development: Normal and Abnormal New York: Oxford University Press Skoczenski AM (2001) Limitations on visual sensitivity during infancy: Contrast sensitivity, vernier acuity and orientation processing In: Rovee-Collier C, Lipsitt LP, and Hayne H (eds.) Progress in Infancy Research, vol Mahwah, NJ: Ablex Wattam-Bell J (1992) The development of maximum displacement limits for discrimination of motion direction in infancy Vision Research 32(4): 621–630 Relevant Websites http://www.pbs.org – PBS http://tinyeyes.com – Tiny Eyes 404 Vygotsky’s Sociocultural Theory Vygotsky’s Sociocultural Theory M Gauvain, University of California at Riverside, Riverside, CA, USA ã 2008 Elsevier Inc All rights reserved Glossary Cognitive socialization – The process by which parents and others ensure that a child’s way of understanding and operating on the world conforms to those deemed appropriate to and valued by his or her culture Community of learners – An approach to classroom learning in which adults and children work together in shared activities, peers learn from each other, and the teacher serves as a guide Cultural-historical – Change associated with the cultural history of a community of people Egocentric speech – A form of self-directed dialogue by which the child instructs herself in solving problems and formulating plans; as the child matures, this speech becomes internalized as inner speech Elementary psychological (or mental) functioning – Psychological functions with which the child is endowed by nature, including attention, perception, and involuntary memory, that emerge spontaneously during children’s interaction with the world Genetic method – An approach to human mental processes that uses developmental analysis; it is based on Vygotsky’s view that these processes can only be understood by examining how they change over the course of growth Guided participation – Learning that occurs as children participate in activities of their community and are guided in their participation by the actions of more experienced partners in the setting Higher psychological (or mental) functioning – Psychological functions, such as voluntary attention, complex memory processes, and problem solving, that entail the coordination of several cognitive processes and the use of mediators Interpersonal (interpsychological) – Psychological experience that occurs across individuals Mediational means – Psychological tools or signs, such as language, counting, mnemonic devices, algebraic symbols, and writing that facilitate and direct thinking processes Microgenetic – Change associated with learning that occurs over the period of a specific learning experience or episode Phylogenetic – Change associated with the evolutionary history of a species Private speech – Internalized egocentric speech that guides intellectual functioning Ontogenetic – Change associated with learning that occurs over the lifetime of an individual Reciprocal instruction – A tutoring approach based on the ideas of the zore of proximal development ZPD and scaffolding Scaffolding – An instructional process in which the more knowledgeable partner adjusts the amount and type of effort he or she offers to the child to fit with the child’s learning needs over the course of the interaction Signs – Language and other conventional forms of representing thought provided by culture that support thinking and regulate interactions between the individual and the world Social construction – An approach to cognitive development in which knowledge is seen as acquired and developed through social processes Tools – Objects or artifacts provided by culture, such as literacy and technology, that support thinking and regulate interactions between the individual and the world Zone of proximal development (ZPD) – The region of sensitivity for learning characterized by the difference between the developmental level of which a child is capable when working alone and the level she is capable of reaching with the aid of a more skilled partner Introduction This article describes the sociocultural theory introduced by the Russian psychologist Lev S Vygotsky (1896–1934), which emphasizes the contributions of the social and cultural world to cognitive development Following a brief description of Vygotsky’s life and the context in which he developed his ideas, the essay describes the distinction made by Vygotsky between elementary and higher mental functions that is important for understanding his approach It then discusses three critical aspects of the approach: the role of mediational means in higher Vygotsky’s Sociocultural Theory psychological functioning, the contributions of social and cultural experience in providing and supporting the development and use of these mediational means, and the primacy of the developmental or, in Vygotsky’s terminology, genetic method This article concludes with discussion of the contemporary influence of these ideas on the study and practice of developmental psychology Vygotsky’s Sociocultural Theory Vygotsky was a leader in the formation of a theoretical approach that emphasizes the contributions of the social and cultural world to intellectual development This approach, which is called the sociocultural or cultural–historical approach to the study of the mind, has had substantial impact on theory and research in cognitive development in Russia since the 1920s The influence of this perspective extended beyond Russia in the early 1960s when the first English translations of Vygotsky’s writings appeared in the book Thought and Language The sociocultural approach draws attention to the role played by cultural tools and signs in mediating thinking and intelligent action It emphasizes how the social world is instrumental in the development and use of these mediational means, and therefore, is a constituent element of human intellectual functioning Three critical aspects of Vygotsky’s sociocultural approach are the role of mediational means in higher psychological functioning, the contributions of social and cultural experience in providing and supporting the development and use of these mediational means, and the primacy of the developmental or, in Vygotsky’s terminology, genetic method This article discusses the theoretical features of this approach, including the distinction Vygotsky made between elementary and higher mental functions that is important for understanding his approach A brief description of Vygotsky’s life and the context in which he developed his ideas provides a useful backdrop for understanding this theory and the research derived from it A Brief Biography of L S Vygotsky Lev Semenovich Vygotsky was born in 1896 in Orsha, a town in the western region of the Russian Empire, to a middle-class Jewish family He was an excellent student in his youth and received many awards From an early age, Vygotsky’s intellectual interests were expansive They included history, culture, social science, literature, philosophy, poetry, medicine, theater, and art Discrimination toward the Jewish community was commonplace in Russia at this time and included quotas at universities for Jewish students However, due to his excellent high school performance and some good fortune, Vygotsky was 405 allowed to attend Moscow University, where he graduated in 1917 with a degree in law While attending the university, Vygotsky also studied psychology and literature at Shanyavskii University in Moscow His postgraduate study was at the Psychological Institute in Moscow, where he received his doctoral degree in 1925; his dissertation was entitled The Psychology of Art In the early 1920s, Vygotsky’s health began a slow but steady decline from tuberculosis, the disease that eventually killed him in 1934 at the age of 37 years At the time of his death, he was the head of psychology at the Institute of Experimental Medicine in Moscow and one of the most prominent Russian psychologists with a large and loyal following of students and colleagues Shortly after his death, Vygotsky’s influence on Soviet psychology, as it was then called, was stalled when the Stalinist regime took hold; Vygotsky’s ideas fell into political disfavor and in 1936, his writings were banned in the USSR Two of Vygotsky’s closest colleagues in the development of his ideas, A R Luria and A N Leont’ev, became prominent psychologists themselves and they helped to sustain and advance Vygotsky’s ideas following his death Stalin died in 1953, and in 1956 Vygotsky’s writings were once again published in Russia and by the early 1960s they were available to scholars outside Russia Despite his short life, Vygotsky was a prolific scholar, he wrote close to 180 articles, essays, and papers, most of which have been translated One of the most significant features of Vygotsky’s personal history for understanding his ideas was the social and political climate in Russia during his time Vygotsky grew up and studied in Russia during a period of tumultuous social change In his youth, Russia was an empire that was ruled by a monarch, Czar Nicholas It included a massive expanse of land and people from many different cultural groups When Vygotsky was young, the social divisions within the society were clearly marked and these divisions had enormous effects on the lives of the Russian people In 1917, the year Vygotsky graduated from Moscow University, the Russian Revolution began and the entire society was in turmoil This revolution was devoted to Marxist ideas and the influence of these ideas on Russian society and intellectual activity following the revolution was enormous Vygotsky, like many other Russian scholars during this period, strived to integrate Marxist ideas into his work As Vygotsky launched his career as a psychologist, civil war and famine ravaged the country and the entire social structure of the nation changed dramatically Many practical social problems plagued this new nation, the USSR, including widespread illiteracy, vast cultural differences among the people of the huge country, and few services for people in need, including children with learning difficulties due to mental retardation or other forms of disabilities Consistent with Marxist ideology, Vygotsky felt that an important role for psychology in this new nation 406 Vygotsky’s Sociocultural Theory was to devise solutions for these types of social problems However, to accomplish this goal Vygotsky needed to create a new form of psychology, one that stretched beyond a focus on individual performance and recognized and incorporated the breadth of human experience that was represented in these pressing social problems Vygotsky’s Approach to Psychological Development The sociocultural approach to cognitive development that is based on Vygotsky’s ideas proposes that mental development is best understood as a product of social and cultural experience Social interaction, in particular, is seen as a critical force in intellectual development It is through the assistance provided by others in the social environment that people gradually learn to function intellectually as individuals In contrast to the emphasis on individual functioning that dominated other trends in psychology of his time, Vygotsky stressed the critical relationship between individual psychological development and the sociocultural environment in which human psychology develops and is expressed He defined the sociocultural environment in very broad terms, including social interaction between individuals, the values and practices of the culture that appear in the routines, rituals, and customs in which people engage, and the tools and signs, most importantly language, that people use to support and extend thinking However, Vygotsky did not view individual psychology or human cognition as a direct consequence of social experience, that is, socially determined He proposed that human development, including cognitive development, is socially constructed That is, in the course of social interaction, the cultural context of development, as instantiated in social behavior and cultural artifacts, and the biological aspects of the human system, including genetic, maturational, and neurological characteristics, create new understandings and capabilities In other words, individual psychological functioning is an emergent property of the sociocultural experiences of the human organism This means that psychological development is a dynamic and constructive process, the outcome of which cannot be known beforehand or by examining the individual and the social context separately from one another Rather, development is generated by the processes that transpire over the course of human social experience in cultural context Vygotsky was particularly interested in social interactions involving more and less experienced members of a culture As these partners collaborate in solving a problem, the more experienced partner assists the less experienced partner, the learner, in ways that support the learner’s engagement in actions that extend beyond the learner’s current individual capabilities In an effective learning situation, this engagement occurs in what Vygotsky called the learner’s zone of proximal or potential development, the region of sensitivity for learning The more experienced partner supports the learner’s activity through the use of signs and tools of the culture As the learner gains competence at the activity, the more experienced partner gradually withdraws support and, in time, the learner comes to function on his or her own in a more advanced intellectual way Thus, the interpersonal becomes the intrapersonal For Vygotsky, what people and learn in the course of collaborative cognitive activity is the foundation of cognitive development and, accordingly, social activity serves as the primary unit of psychological analysis in this approach Like other students of developmental psychology, Vygotsky was interested in the products or outcomes of development However, his main focus was on the processes that underlie and motivate development He considered development as a process of qualitative change, specifically one in which change occurs in the mediational means that an individual uses to understand and act upon the world Vygotsky was especially interested in changes that occur when elementary mental functions, such as basic perception and involuntary memory, are transformed into higher mental functions, such as reasoning and voluntary memory For Vygotsky, higher mental functions, which he considered the hallmark of human intelligence, are the result of the transformation of basic cognitive abilities into mental processes that are capable of devising and carrying out conscious goal-directed actions Social and cultural phenomena are instrumental to this development For instance, the elementary form of memory, which is similar to perception and largely composed of images and impressions of events, is an unintentional and direct mapping of features of the environment As children develop, they learn to use psychological signs and tools, like language and literacy, to elaborate and extend this basic memory function into a more deliberate and explicit form Children not need to devise the psychological signs and tools that support higher mental functions; they already exist in the culture However, children need to learn about these signs and tools and how to use them effectively to support or mediate cognitive processes and carry out goal-directed actions, like intentional or voluntary memory Children learn this information through the assistance of people in their culture who are experienced in the psychological signs and tools that support thinking Some of this learning is informal, emerging from the everyday experiences and interactions children have, and some of this learning occurs in more formal societal settings, such as school Both formal and informal arrangements of learning involve signs and tools that reflect the broader cultural context Vygotsky was interested in a range of mediational means, both symbolic and material, including language, mathematics, mnemonic devices, artistic symbols, and Vygotsky’s Sociocultural Theory literacy For Vygotsky, when people learn how to use and eventually adopt signs and tools that support thinking, the fundamental nature of thinking changes Furthermore, mediators not only support and extend an individual’s intellectual functioning, they also connect the individual’s thinking and action with the social and cultural context that devised and provides these mediational means With the assistance of more experienced partners, children develop their cognitive abilities in ways that are useful for solving the types of problems that are deemed important in the cultural setting in which they live More experienced members of a culture, primarily family members, teachers, and older children, convey many important things about the mind and how to use it, including the types of problems that are important to solve, ways of approaching these problems, and how to use the material and symbolic tools in the culture to solve these problems Language assumes great importance in this theory; it operates as the primary medational means by which social partners communicate information to each other and that individuals use to guide their own goal-directed actions Thus, according to Vygotsky, cultural tools and signs not only support the development and use of higher mental functions, they transform elementary mental functions and, in doing so, enable thought and action that would not be possible without the use of these tools The adoption of these tools of thinking and the social methods through which they are learned also has the broader cultural consequence of aligning the child’s thought and action in ways that are consistent with those that are practiced and valued by their culture This developmental course provides a method of ensuring that new members of a culture develop the skills needed to become competent mature members of the community In other words, children develop the skills that are suited to the types of problems, ways of thinking, and incorporate the valued tools and practices of their culture Elementary and Higher Mental Functions Vygotsky distinguished two general forms of mental functioning: those that are biologically based and innate, which he called elementary mental functions, and those which he called higher mental functions that emerge from social and cultural experience Basic psychological functions are shared with other primates whereas higher mental processes are unique to humans and cognitively complex, that is, they draw on and integrate many intellectual abilities Although they build on the elementary forms, higher mental functions are qualitatively different in that they are mediated by the social and cultural world through sign 407 systems (e.g., language and mathematics), cultural tools (e.g., literacy and technology), and more experienced cultural members who convey to children ways of using these powerful mental abilities Thus, higher mental processes are not simply more complex versions of elementary functions that can be accounted for solely by biological laws Higher mental processes are qualitatively different in that in addition to biological laws, they also rely on historical laws or principles that are instantiated in cultural values and practices and mediated by signs, tools, and cultural participants A discussion of memory processes illustrates the difference between these two types of mental functions The elementary form of memory is constructed of images and impressions of events This type of memory is very close to perception in that it is unintentional and the environment directly influences its content The higher form of memory involves the use of signs to mediate memory functions intentionally and then uses memory to carry out a complex and conscious goal-directed action; for instance, an individual may write something down to remember it for later use or to communicate this information to others In this example, literacy is used as a tool to elaborate on or extend the natural functioning of memory and it enables the actor to carry out an activity that would not be possible without the mediational means Although this mediated example includes literacy, and therefore would apply to cultures in which literacy is present, there are many examples of mediated memory from nonliterate cultures For example, the Quipu, which was devised and used by the ancient Incas in the land that is now Peru, was an elaborate set of knotted cords used to record important information about the community such as census figures, tax schedules, and the output of gold mines Four significant changes in intellectual functioning occur when elementary mental functions are transformed into higher mental functions First, there is a shift in the control or regulation of behavior from other-regulation to self-regulation Natural or basic mental functions are responsive to conditions in the environment, for example, involuntary memory in the form of eidetic images In contrast, voluntary memory entails active effort by the individual to remember some information in the world To encode and remember this information, the individual employs skills that support memory, such as selective attention and memory strategies like rehearsal and organization Second, voluntary memory is conscious The individual knows that a mental process, in this case memory, is being used A third important feature of the distinction between elementary and higher mental functions is that the latter has social origins Although elementary mental functions are natural, biological forms, higher mental functions are socially constituted Finally, signs and tools of thinking mediate higher mental functions, a concept which scholars, such as J V Wertsch, who study Vygotsky’s ideas consider 408 Vygotsky’s Sociocultural Theory to be the most important and unique contribution of this approach to intellectual development Cognitive Mediation through Signs and Tools The use of signs and tools to mediate human mental functioning was, for Vygotsky, the single distinguishing feature of human intelligence Whereas other primates, and human beings when they use basic mental functions, react to and use external features of the world to guide action, human beings are also capable of creating signs, such as language and number systems, and tools, such as navigational systems and computer technology, that affect how people think and interact with the world In other words, human beings create and live in an organized social unit, called culture, which devises signs and tools for supporting and extending human thinking and action For Vygotsky, this capability transforms the nature of human intelligence; it frees it from its biological base and creates what is referred to as a cultural mind Moreover, cultural signs and tools are passed across generations from more to less experienced members of the group Children cannot devise these tools nor can they learn about them on their own Rather, they learn about them and how to use them from people who are more experienced in their use In short, higher mental functions have sociocultural origins Culture, both through its members and via the artifacts in which it is represented, provides mediational means that enable the development of higherlevel cognitive skills In this way, culture and social experience transform basic mental functions into higher-level cognitive functions Signs and tools are not static They change over time in how they mediate an individual’s actions as new capabilities, interests, and demands emerge They also change across generations as culture changes and confronts new types of problems and concerns Thus, the incorporation of signs and tools into mental functioning that transforms basic cognitive abilities into higher and more complex forms reflects temporal or historical experiences of the child and the culture Vygotsky emphasized that this is a psychological and not a sociological process The social world and its changes are manifested psychologically Cultural signs and tools exist, that is, they are meaningful, by operations that occur inside individuals In development, these signs and tools are initially experienced interpsychologically With time and experience they become intrapsychological as individuals learn to use them to accomplish goal-directed action It is significant that these signs and tools are not arbitrary, but stem from an organized and historical system, culture, and thereby contain psychological connections to other societal members and to cultural ancestors When new societal conditions and problems emerge, ways of adapting must be crafted and these adaptations build upon prior forms This process implies that full understanding of any current psychological form requires sensitivity to the individual, social, and cultural– historical forms that helped shape them What is important in Vygotsky’s conception is that signs and tools are not merely external forces or stimuli to which children learn to respond Signs and tools carry meaning and it is the meaning itself that is learned and adopted by children For example, language is one of the primary sign systems that children learn For language to contribute to cognitive development more broadly, children must learn more than just how words can be associated with particular objects or actions Rather, they learn the meaning of words, which contains the essence of the word, such as the object of reference, along with its significance and place in the child’s social world, for example, how important this object is, how it relates to other objects, and so forth Participation in this meaning system allows the child to engage with others in meaningful, goal-directed ways as well as interpret and act upon the world in ways that make sense to other people and in their developmental context Contributions of the culture to cognitive development are evident in the mediational role of signs and tools in guiding and supporting thinking and intelligent action This mediational role is conveyed to children largely through social interactions with other people, especially more experienced cultural members Cultures also provide institutions and more formal social settings, such as rituals, that facilitate cognitive development Formal institutions, such as school, significantly alter the ways in which people in a community think by emphasizing and providing access to particular and highly valued mediational forms School is designed to promote and support the development of particular approaches to solving problems, including the use of certain signs and tools that aid problem solving Less formal social institutions and social settings also influence cognitive development For example, in cultures in which verbal explanation is highly valued, cultural practices related to this value such as oral narratives and story telling assume much importance and are part of children’s everyday experience and cognitive development in that community Consistent with Vygotsky’s formulations, as cultural signs and tools become an intricate part of intellectual activity, it can be difficult if not impossible to discern where the tool ends and the mental activity begins The anthropologist G Bateson offered an example that helps explain this point When a blind man uses a walking stick, the man uses vibrations from the stick when it hits the ground to guide his steps Where does the man’s thinking about or perception of the ground begin? At the tip of Vygotsky’s Sociocultural Theory the stick where it touches the ground, where the hand and stick meet, or when the vibrations travel through the nervous system and reach the man’s brain? As this example shows, when a tool is intimately tied up with a mental activity, it is part of the mental activity and all attempts to describe the activity by dissecting it into its component parts are doomed to fail Note especially that the tool in this example, the walking stick, has no content or cognitive meaning separately from the blind man’s activity This is an important point Oftentimes signs and tools that have been devised to support thinking are viewed as embodying the cognitive activity However, from Vygotsky’s point of view, this is not true And following up on this view, it is not surprising that Vygotsky believed that the most important knowledge humans possess is the knowledge of different ways or means for organizing and using mental processes in specific circumstances – the very type of knowledge that is embedded in communally held practices and transmitted across generations by people who engage in and value these practices Vygotsky’s view of the cultural contributions to human intelligence suggests that any attempt to assess children’s cognitive development must consider the cultural context as a critical force If the culturally specific nature of children’s learning is ignored, he claimed that one runs the risk of seriously underestimating children’s development Indeed, many cross-cultural studies have documented that children learn highly sophisticated and complex cognitive skills that are important in their culture More experienced cultural members play significant roles in this process of cognitive socialization because they function as the most immediate representatives in children’s lives of the mediational means to support thinking Researchers have studied several social processes that promote children’s learning of culturally valued skills, such as observational learning, the social regulation of attention in infancy, deliberate efforts to transfer knowledge from more to less experienced partners, social coordination during joint cognitive activity, and cognitive socialization through conversation and joint narratives Taken together, this research suggests that social opportunities for children’s learning appear in many forms and that culture determines the frequency and manner with which these processes occur Vygotsky’s theory leads us to an appreciation of different cultures and their values, and connects cultural values and practices directly to cognitive development Language plays a central role in Vygotsky’s sociocultural approach The acquisition and use of language is a primary component of children’s developing intellectual abilities in a social context because language provides children with access to the ideas and understandings of other people It also enables children to convey their own ideas and thoughts 409 to others Moreover, with development, language, which is a cultural product, comes to mediate individual mental functioning In other words, as children learn to use language, it gradually becomes incorporated into their thought processes and, as a result, it both facilitates and constrains thinking For Vygotsky, thought and speech are independent in early development However, around the second year of life they join together when children begin to use words to label objects Within year, speech assumes two forms: social, or communicative, speech and egocentric speech (also called ‘private speech’) For Vygotsky, egocentric speech is a form of self-directed dialog by which the child instructs herself in solving problems or formulating plans Thus, egocentric speech becomes a tool for intellectual growth and allows the child to become a more effective and skilled learner By age or years, this form of speech becomes internalized in the thought process and becomes inner speech, that is, a form of speech that becomes internalized as thought Thus, language serves as an aid for regulating cognition as well as a tool for communicating What is important to stress about Vygotsky’s idea of mediation is the role it plays in development Although Vygotsky did not outline or seek to define stages of development, he did see development as a process of qualitative rather than quantitative change The types of qualitative changes he outlined were the result of changes in the forms of mediation that are used Mediational means, both through signs or tools, function to inhibit direct and impulsive responses and facilitate the use of more consciously regulated and deliberate (or thoughtful) ways of operating on the world For Vygotsky, these mediational means free human beings from a solely biologically based course of development and create a new, culturally based process of psychological development For instance, before infants learn to use language, they have knowledge and carry out intelligent actions But these processes are unmediated by language and, therefore, are absent of certain types of mental functioning that language supports Encoding an object in a form that draws on linguistic conventions, such as grouping the object with other objects or with actions in ways that have meaning in the culture, transform how the child processes and remembers the object This transformation serves many ends It links the child’s experience with the experiences of other people, it enables the child to communicate with others about the object, and it exists in the child’s memory in a way that is amenable to reflection and reevaluation, albeit within a framework afforded by the cultural-linguistic system through which it was encoded and retained The idea that development is evident in the mediational means that are used to organize and support thinking was pivotal to Vygotsky’s developmental method 410 Vygotsky’s Sociocultural Theory It directed his attention to the social experiences in which children learn these mediational means It also allowed him to conceptualize development at multiple levels, including ontogenetic, phylogenetic, cultural–historical, and microgenetic The Role of the Social Experience in Psychological Development Because of his interest in the social origins of intellectual functioning, Vygotsky was less concerned with children’s individual intellectual capabilities at any particular point in time than he was with the child’s potential for intellectual growth through social experience To assess this potential and to understand how intellectual development occurs, Vygotsky proposed the notion of the ‘zone of proximal development’ (ZPD), which he defined as the difference between a child’s ‘‘actual developmental level as determined by independent problem solving’’ and the child’s ‘‘potential development as determined through problem solving under adult guidance or in collaboration with more capable peers.’’ The child’s ZPD is not static Although the zone or region of sensitivity to learning is defined initially by the child’s existing knowledge or competence in an area of intellectual growth, with proper support for learning the child’s level of competence in this area changes, and the child’s ZPD changes accordingly The concept of the ZPD is twofold First, it represents an alternative approach to the assessment of intelligence – examining children’s intellectual potential under optimal conditions, that is, conditions that are tailored to the child’s specific learning needs and that build on the child’s present capabilities These ideas were especially relevant to Vygotsky’s research in educational psychology and his concern with designing programs that could support the unique learning needs of children with disabilities or with mental retardation Second, the ZPD represents a way of understanding how children’s intellectual development occurs through social interaction with more skilled partners As such, it builds bridges between the mind of the individual child and the minds of others According to Vygotsky, working within a child’s ZPD – that is, with the assistance of an adult or more experienced peer – allows the child to participate in the environment in more complex and competent ways In other words, in social interaction targeted toward the child’s ZPD, a child has the opportunity to engage in more advanced cognitive activities than the child could undertake alone This is because more experienced partners are able to break down an activity into component parts to make it more understandable and accessible to the learner More experienced partners also help the learner by modeling new strategies for solving the problem and by encouraging and supporting the learner’s involvement in the more complex components In this process, the learner is introduced to and has opportunity to use signs and tools devised by the culture that support thinking Finally, the more experienced partner may take on or assume some of the more difficult task components so that the learner can concentrate on other aspects For example, an adult may keep track of what has been done so far in the problem or in relation to the goal so that the child can concentrate on the next immediate step Even though children learn from various types of social arrangements, Vygotsky’s perspective on the social contributions to cognitive development more closely matches the types of interactions children have with adults than with peers Because adults are more experienced than peers with many of the skills involved in informal instructional situations, such as turn taking and creating an overall plan for the activity, adult assistance is often superior to that given by peers Of great importance is the child’s active involvement in the interaction and the solution, which adults often verbalize and which fosters the child’s understanding Vygotsky’s theory has had considerable impact in the fields of psychology and education For example, ‘scaffolding’, a form of instruction inspired by Vygotsky’s ideas, is the process by which the more experienced partner or teacher adjusts the amount and type of support provided so that it fits with changes in the needs of the learner over the course of the interaction By careful monitoring of the child’s progress, the teacher adjusts the task to make it manageable for the child and provides assistance when needed In scaffolding, which has been demonstrated in a variety of tasks, the teacher gradually reduces the amount of support he or she provides as the child becomes more skilled, so that eventually the child can execute the task in a skilled fashion independent of the partner’s help Other applications of Vygotsky’s ideas to educational practice appear in the method of ‘reciprocal instruction’, introduced by A Palinscar and A Brown This approach enhances children’s reading comprehension by having the learner work in close and supportive collaboration with more experienced partners who help children develop skills critical to comprehension, such as explication and elaboration A Brown and her colleagues also introduced another related classroom application called the ‘community of learners model’ In this approach, adults and children work together in shared activities, peers learn from each other, and the teacher serves as an expert guide who facilitates the processes by which the children learn The teacher uses the technique of scaffolding to support children’s learning and the students, who vary in knowledge and ability, actively help each other learn through their interchanges A way of describing children’s informal learning experiences outside of school situations called ‘guided participation’ was introduced by B Rogoff; it too is derived from Vygotsky’s ideas Guided participation Vygotsky’s Sociocultural Theory highlights the fact that adults regularly support learning in the context of everyday activities by directing children’s attention to and involvement in these activities Sometimes these activities are child focused, such as in play or an organized game, but oftentimes they are adult activities in which the primary purpose is not to instruct children but to carry out the activity itself In these situations, adults support children’s involvement in specific but meaningful ways For example, as a mother tries to make a cake her child may ask if he can help The mother may agree and then structure the task in a way that gives the child some real responsibility in the activity Over time, if the child remains interested in and continues to be involved in the activity, the child’s and mother’s participation will both change as the child’s competence increases Furthermore, as the child’s roles and responsibilities change, the child’s understanding of the activity also changes As in Vygotsky’s approach, the child is not merely a passive learner who follows the instructions or prompts of the more experienced partner Rather, the child is a full and active participant who co-constructs with the partner, new ways of understanding and learning an activity For Vygotsky, the most significant aspect of social interaction for mental development is the fact that social experiences convey to children the mediational means for adapting basic cognitive abilities to higher cognitive functions According to M Cole, this view recasts the traditional dichotomy of nature versus nurture by proposing that it is human nature to nurture and that it is through nurturing that the individual mind grows Vygotsky’s view of the social processes that support cognitive development is broad in conception Although he proposed specific processes of social interaction that are instrumental to intellectual development, he also emphasized other historical processes that are integrated with mental functioning and its development in his genetic method Vygotsky’s Developmental or Genetic Method For Vygotsky, the developmental method is the central method of psychological study Vygotsky’s interest in the processes of development led him to focus on dynamics of change, both within an individual, as captured in the idea of the ZPD, and in a culture, represented in its history and instantiated in the signs and tools that are used to organize and guide intelligent action In contemporary psychology, the concept of development is primarily used to refer to child or adolescent development or in some cases to development in adulthood Although the sociocultural approach has important views on and implications for understanding and studying development from this vantage, it is seen as only one of the ways in which development 411 can be integrated in a meaningful way in psychological analysis As M Cole and S Scribner pointed out, Vygotsky’s abiding concern with the origins and development of human consciousness and behavior across generations and through process of human evolution reflects his broad conception of development This stance is consistent with his view that psychological functioning can only be understood if it is observed in the process of change For Vygotsky, the outcome of any psychological process is not predetermined, it emerges from the complex social–biological dynamics inherent to the situation in which learning occurs For instance, the same conditions of learning will lead to very different outcomes for a child with a learning disability compared to a child without a learning disability Vygotsky emphasized that human psychological growth is a product of the social and cultural history of an individual He was interested in four different ways in which history contributes to the development of higher mental functions: general cultural history, ontological history, the history of higher psychological functions, and the history of a particular learning experience ‘General cultural history’ includes aspects of human social life that represent collective means of acting and thinking, such as material resources or tools that support thinking and socially organized activities and institutions in which intelligent actions occur These aspects of social life, which are passed across generations, regulate human thinking and behaving ‘Ontological history’ is a person’s individual or life history It includes the integration of biological processes that regulate the development of basic mental functions, such as perception and practical tool-based intelligence, and sociocultural processes that regulate the development of higher mental functions, such as voluntary memory and language acquisition The ‘history of higher mental functions’ examines how specific mental functions, such as remembering, classifying, and conceptualizing, have changed over human history as they have adapted to the circumstances and environments in which people live The ‘history of a particular learning experience’ includes change at the microanalytic level and is captured in the processes described in relation to the ZPD The genetic method requires analysis that stretches beyond the conventional boundaries of psychology Its formulation was undoubtedly aided by the expansive scope of Vygotsky’s own intellectual interests and background Vygotsky recognized that examining any psychological phenomena at all these historical levels is a huge effort However, he was concerned that ignorance or confusion about these various levels and their roles in human psychological experience could lead to a misinterpretation of psychological phenomena Vygotsky’s rejection of any form of reductionism stems from the complexity of this view of development He did not believe that any single factor or set of explanatory principles could explain all of mental functioning and its development He was 412 Vygotsky’s Sociocultural Theory critical of reductionist views of his time, such as Behaviorism, as well as theories that were broader in scope but nonetheless posited single explanatory forces for psychological functioning, such as Gestalt psychology with its emphasis on structural forms Vygotsky emphasized the multiple forces underlying psychological phenomena and he argued that these forces were only apparent when they were ‘in motion’, that is, in the process of change or development Summary and Conclusions Vygotsky’s approach emphasizes the culturally organized and socially mediated nature of human cognitive processes This perspective offers a view of cognitive development within the contexts in which this development actually occurs and, as such, it overcomes some of the limitations to theories that focus solely on the individual or on the environment Vygotsky’s theory has helped to make developmental psychologists more aware of the importance of the immediate social contexts of learning and cognition In particular, through the notion of the ZPD and the related concepts of scaffolding and guided participation, this approach has pointed to new ways of assessing children’s cognitive potential and of teaching reading, mathematics, and writing Moreover, Vygotsky’s approach has increased appreciation of the importance of culture in cognitive development Vygotsky’s theory also provides a way of conceptualizing the role played by sign systems and tools of thinking in cognitive development This theory addresses how tools such as literacy and numerical systems, which are products of culture, get passed on across generations and become incorporated into the ways children learn to think and solve problems as they grow Limitations of this approach largely pertain to its lack of specification of processes of ontogenesis in cognitive development Although the approach emphasizes change over time in a specific learning experience, or microgenesis, and the role of long-term historical influences on intellectual development as embodied in cultural practices, signs, and tools, Vygotsky was not specific in terms of age-related changes Furthermore, like many other cognitive theories, this approach does not describe how changes in social and emotional capabilities contribute to changes in children’s cognitive capabilities Nor is it clear how cultural contexts that are available to children at different points of development support and promote cognitive change Over the last two decades educational programs that draw on Vygotskian and socicocultural views have increased In these programs more knowledgeable people, especially teachers, play critical roles in arranging and supporting children’s learning using techniques like scaffolding, collaboration, and the provision of tools that support learning and thinking In the main, these approaches have been successful in demonstration programs Although Vygotsky’s own ideas were informed by practical social problems, especially those pertaining to education, adapting sociocultural ideas to classroom practice beyond demonstration programs remains a challenge In part this is because there are few systematic descriptions of cognitive development in specific academic domains that incorporate in a central way the social basis of the development and expression of these abilities and skills There is also limited understanding of how social experience before children enter school supports the development of cognitive abilities that are important in the classroom It is also unclear how to calibrate or scale up the social learning processes based on sociocultural ideas that have been identified in controlled laboratory research to the demands and complexity of the classroom environment Finally, the adaptation of these ideas to classrooms with diverse populations of students presents a unique set of difficulties The sociocultural approach does suggest that language skills are central to cognitive development These skills serve as the medium of information exchange and as a way of organizing and representing knowledge in the head Ensuring that children have the language skills to access the social learning experiences of the classroom is vital, especially for language minority students who are at high risk of academic failure Vygotsky left developmental psychology a unique and valuable legacy of ideas His approach to the development of the mind steers the field of psychology toward an entirely different set of questions than can be found in other contemporary theories of cognitive development The depth and breadth of Vygotsky’s thinking have led psychologists, such as J Shotter, to characterize Vygotsky as a ‘complete psychologist’ in that he tried to conceptualize human development along every dimension of psychological functioning Although Vygotsky worked almost a century ago, he concentrated on issues that are important to developmental psychology today, such as the complex and dynamic nature of cognitive development, the inherent links between internal and external forces in development, and qualitative changes in mental functioning as children grow His unique emphasis on mediational means as central to intellectual development provides a cornerstone for contemporary research in a wide range of areas including language development, social cognition, problem solving, educational psychology, child socialization, and cultural psychology See also: Cognitive Development; Cognitive Developmental Theories; Reasoning in Early Development; Symbolic Thought Vygotsky’s Sociocultural Theory Suggested Readings Cole M (1996) Cultural Psychology: A Once and Future Discipline Cambridge, MA: Harvard University Press Kozulin A (1990) Vygotsky’s Psychology: A Biography of Ideas Cambridge, MA: Harvard University Press Luria AR (1978) The Making of Mind: A Personal Account of Soviet Psychology Cambridge, MA: Harvard University Press Moll LC (1990) Vygotsky and Education: Instructional Implications and Applications of Sociohistorical Psychology New York: Cambridge University Press Rogoff B (2003) The Cultural Nature of Human Development New York: Oxford University Press Van der Veer R and Valsiner J (1991) Understanding Vygotsky: A Quest for Synthesis Oxford, UK: Basil Blackwell 413 Vygotsky LS (1978) Mind in Society: The Development of Higher Psychological Processes Cambridge, MA: Harvard University Press Vygotsky LS (1987) Vygotsky’s sociocultural theory In: Rieber RW and Carton AS (eds.) The Collected Works of L S Vygotsky, Vol 1: Problems of General Psychology New York: Plenum Wertsch JV (1985) Vygotsky and the Social Formation of Mind Cambridge, MA: Harvard University Press Relevant Website http://www.marxists.org – Lev Vygotsky Archive; Lev Vygotsky – Thinking and Speaking ... months of life manifestations of voluntary control of the facial muscles that are used to smile and eat, and subsequently the control of neck muscles, the voluntary use of the hand, the ability of. .. appears between 34 and 37 weeks; head turning in response to light appears between 32 and 36 weeks Fullblown walking and crossed extensor reflexes appear only between 35 and 37 weeks After birth,... in early childhood He is currently Honorary President of the World Association of Infant Mental Health and serves on the Board of Directors of Zero To Three Hill Goldsmith is Fluno Bascom Professor