Growing Points in Developmental Science

An Introduction

Willard W. Hartup, Rainer K. Silbereisen

• Publisher: Psychology Press
• Year: 2005
• ISBN:
  9781135425616
• Edition: 1
• Topic: Psychology
• Subtopic: History & Theory in Psychology
• Index: Psychology

Growing Points in Developmental Science is an ISSBD publication based on the millennium symposia papers published in the International Journal of Behavioral Development in 2000. This collection of overview chapters summarises the state of the art and the way forward for this discipline.
Experienced researchers as well as younger, cutting-edge scientists have contributed to this international collection. The topics range from early experience to old age, and include issues in both social and cognitive development. Particular interests are investigated, such as the biological substrates of behavioural development, early experiences in terms of both basic and applied science, and cross-cultural contexts of development. Personality, knowledge and the acquisition of memory are also considered. In each case, the authors survey the history and traditions that have marked their research areas, as well as the current status and outlook.
Growing Points in Developmental Science represents expert wisdom rooted in a bird's eye view of the trends and controversies that have helped to shape the discipline, its contributions to science and its application. It is intended as a resource for scientists of different generations interested in developmental science, and will appeal to advanced students and young investigators as well as seasoned researchers.

1 Motor development as foundation and future of developmental psychology

Esther Thelen

Indiana University, Bloomington, USA

Human infants are born with very little control over their bodies. Yet within a year or so, they are able to sit, stand, walk, reach, manipulate objects, feed themselves, gesture, and even speak a few words. A year later, toddlers are adept at running, climbing, scribbling, riding a tricycle, and talking in simple sentences. For parents, these new motor skills are the most dramatic and visible changes in the first few years of life, frequently noted and commented upon. For those interested in studying developmental processes, this sequential unfolding of motor milestones is like a open window on change. Whereas children’s mental lives must be measured indirectly, their movements are continuously observable. Each new pattern is there to see and describe. There are no hidden processes between the control of the movement and its actual execution.

MOTOR DEVELOPMENT: THE GOLDEN AGE

It is no surprise, therefore, that the emergence of motor skills has figured so prominently in the first scientific studies of human development, truly laying the foundation of the field. Rich description of infant movement dates to the last century with Darwin’s (1877) well-known “biography” of his own child and the pioneering work of the German physiologist Preyer (1888), and the tradition was continued into the twentieth century with the narratives of Millicent Shinn (1900). The full flowering of the descriptive work in motor development began in the 1920s with the publication of the first of Arnold Gesell’s pathbreaking research and popular monographs (e.g., Gesell, 1928; Gesell & Thompson, 1934). The golden age continued through the 1930s with Mary Shirley’s (1931) exquisite longitudinal descriptions of 25 infants, Myrtle McGraw’s (1935) well-known and still contentious study of the twins Jimmy and Johnny, and Nancy Bayley’s Berkeley Growth Study (1935). In 1946, Carmichael’s Manual of child psychology contained two seminal articles by Gesell (1946) and McGraw (1946), attesting to the theoretical status of motor studies in the field.

There were three important and related legacies from this golden age of motor development research. The first legacy from these pioneers is their theoretical contributions, and especially their strong grounding of human development in biology. The second is empirical through the introduction of detailed and rich description, novel methods for capturing human movement, and clever natural experiments. The third, and perhaps the most enduring, was the establishment of developmental norms. I discuss each of these legacies in turn.

The legacy of development grounded in biology

The two most important theorists of this era were Arnold Gesell and Myrtle McGraw. Both provided us with massive descriptions of early motor development. But for both scientists, the motor catalogues were not the ends in themselves. Rather both Gesell and McGraw saw these descriptions as a way to understanding the most general, and profound, developmental principles.

Gesell and the dynamic principles of growth

Gesell left us the most well-articulated and comprehensive developmental theory, one that is still insightful and attractive (for many details, see Thelen & Adolph, 1992). From the start of his career, Gesell claimed deep roots in the science of biology. He viewed development as a unitary process, requiring description at many levels encompassing evolution, embryology, comparative psychology, neurophysiology, and anthropology. He was especially influenced by Charles Darwin, whom he considered the founder of the scientific study of the child, and by G.E. Coghill, an early behavioural embryologist. Gesell attributed to Darwin his core belief that mental life is continuous with, and impelled by, the same processes that drive all organic growth. Moreover, Gesell admired Darwin’s naturalistic methods, and he saw himself, too, as a naturalist, “tirelessly” seeking “ideological order” though relentless observation and comparison (Gesell, 1948, pp. 36-37). From Coghill, Gesell learned, first, that development was a morphological process, that is a change in the form of behaviour. Gesell believed that, just as movements and postures provided a read-out of the nervous system, so even mental development had this morphological character, that is, it could be understood though observable behaviour. Second, Gesell was convinced that principles of growth and development illustrated by Coghill’s (1969) studies of the salamander were the same for all species, including humans. “We believe that the growth processes which mold the body and behavior of the human infant are in essence comparable with those which are being successfully analyzed by experimental embryology,” he claimed (Gesell & Thompson, 1938, p. v). This led to Gesell’s third legacy from Coghill, the view that behavioural changes followed biologically driven neural maturation, and not the other way around. Gesell’s maturationist views stemmed directly from Coghill’s discoveries that, in the salamander, changes in movement patterns emerged from neural events that happened before sensory connections were made¹. Movements, therefore, were a product of autonomous neural changes, not from the sensory input.

The practical importance of Gesell’s theory was to act as a counterweight to the popular notions of behaviourism that were fashionable at that time. To parents who were told that infants were totally shaped by their environments, Gesell offered a different view, one of an autonomous unfolding of potential. The role of the environment was to support this unfolding, but it did not engender it. Thus, there was no point of training or teaching children until they were developmentally ready.

McGraw and the biology of development

Myrtle McGraw was also a developmentalist of great sophistication and subtlety who used human motor skill development as her principal empirical data. Although McGraw believed strongly in the ultimate inseparability of structure and experience, she expressly designed her study of the twins Jimmy and Johnny (McGraw, 1935) to ask which of their early motor skills could be trained and which were more fixed by developmental design. One twin, Johnny, was exercised daily in a variety of skills, both universal (sitting, walking) and cuturally specific (swimming, roller-skating). She discovered that while training had some effects on the quality and initial performance of Johnny’s movements, in the long run, intensive training did not make a big difference. These results were taken up by the popular press as refuting associationism and supporting the primacy of maturation. Bergenn, Dalton, and Lipsitt (1992) claim that McGraw’s legacy as a maturationist oversimplifies her more sophisticated view of development. They are probably correct, but the twin study, plus her subsequent work on the development of locomotion, put the role of maturation into the forefront.

The legacy of methodology

From our technology-rich vantage point, we can only stand in awe of the detailed data so cleverly and painstakingly collected by the early movement pioneers. In addition to photographs and movies, analysed in great detail, they also recorded movement directly. For instance, Burnside (1927) and Shirley (1931) recorded infants’ and toddlers’ footprints by oiling the children’s feet and allowing them to walk on paper. Many critical parameters of gait can be measured by this simple technique, and indeed it is still being used today (Adolph, 1997). Another methodological advance, important in the establishment of developmental norms, was repeated testing of the same children in a large number of standardised tasks. Gesell took this testing to high art, with highly standardised equipment, structured interviews, and detailed instructions to the testers (Gesell & Thompson, 1938).

The legacy of developmental norms

The legacies of theory and of measurement are closely tied to the third, and perhaps most lasting, influence, that of developmental norms. Although mental testing of children dates back to the early part of the century, largely through the work of Alfred Binet, it was Gesell who brought the concept of developmental norms for infants and young children into the mainstream of developmental psychology, into the popular psyche, and into the homes of millions of parents. The test battery that Gesell and his staff perfected in the 1920s and 1930s still forms the basis of the most widely used infant tests today, the Bayley Scales of Infant Development and the Denver Developmental Screening test. Today such tests are so universally accepted that their origins are little discussed. But it was Gesell’s theoretical insights and methodological rigour that led to the vast catalogue of motor milestones upon which these tests were based.

Gesell, like Coghill, saw in the postural and movement forms a direct reflection of the internal, lawful processes of growth. The link to collecting normative data on infant movement was a direct one (Gesell & Thompson, 1938, p. 4):

the underlying concepts of the normative study may be summed up as follows: Behavior grows. Growth expresses itself in ordered patterns. Behavior growth, like physical growth, is a morphosis. It is a process which produces a progressive organization of behavior forms.This morphogenesis can be investigated by morphographic methods and especially by analytic cinematography. By these methods we can ascertain the lawful sequences and norms of psychological growth for the purpose of genetic research. These norms may also be used as standards of reference for the analytic appraisal of development status.

The idea that by a particular age, an infant or toddler “should” have achieved a particular motor milestone has not only become a standard developmental diagnosis, but it has also become completely entrenched in our cultural beliefs about child-raising. For instance, I own a used copy of Gesell’s The first five years of life (1945), which was originally a gift from “Mother Dingle” to the “Dunlaps” with the loving inscription, “Please read from cover to cover.” This book is one of many written by Gesell which sets normative standards of behaviour based on his observations, and we can imagine the Dunlaps scrutinising their child at each age for “typical behaviour” in each “typical day”.

In sum, the golden age of motor development left us with a rich heritage: a deep understanding of growth and form, an appreciation for the interweaving and nonlinear course of development, a sense of our biological continuity, and exact scientific methods. What happened to that legacy?

MOTOR DEVELOPMENT: THE DORMANT TIMES

After more than two decades of extraordinary theoretical and empirical contributions to our understanding of development, the study of motor systems had declined by 1950 and then lay dormant for nearly 30 years afterward. This dramatic reversal of fortunes can be attributed both to the state of the field itself and to changes occurring in psychology as a whole.

As I have suggested previously, it may be that the successes of the early pioneers also contributed to the decline of the field (Thelen, 1995). They produced vast and widely published catalogues of motor milestones and richly detailed descriptive studies. The norms were incorporated into developmental tests and became family lore, at least in middle-class North American families. There seemed to be little left to do. Moreover, both Gesell’s and McGraw’s theoretical positions appeared to lead to dead ends in terms of further empirical studies, but for different reasons. Once Gesell showed, through the descriptive topologies of behaviour, that human development obeyed universal principles, the case was effectively closed. For McGraw, the situation was more complex. She admitted in her 1962 foreword to The neuromuscular maturation of the human infant that she did not achieve her goal of relating the development of function to the maturation of structure. Part of the problem was that methods for studying changes in the brain were inadequate. But she also recognised that the earlier theoretical formulations were too simplistic, especially the division of behaviour into cortical and subcortical influences, and the neat separation of “instincts” vs. “acquired traits” or “maturation” opposed to “learning” (McGraw, 1945/1973).

The decline of motor development must also be understood in light of the other forces in the field during the 1950s, 60s, and 70s. During this time, learning theorists and experimental psychologists dominated academic departments of psychology. Descriptive and normative data, no matter how detailed, could not be compared in apparent “scientific rigour” to the tightly controlled experimental methods practised by these disciplines.

At the same time, the focus in developmental psychology shifted dramatically. The work of Jean Piaget became increasingly well known and highly influential, igniting fervent interest in the inner mental life of children (as opposed to the form of their overt behaviour). Piaget offered descriptive stages, but he also inspired brilliant experimentation, something that the motor development theorists did not do. The lesson may be that even the most elegant theory survives only as it generates new and copious empirical research.

MOTOR DEVELOPMENT: TWO DECADES OF REBIRTH

Beginning in about 1980, the tide began to turn again, and interest in movement gradually gained momentum. Just as multiple factors contributed to its decline, the field’s revitalisation has come from a number of converging influences. These included several theoretical advances: new ideas in movement science and biomechanics, insights from ecological psychology, and the import of dynamic systems theory. But the field has also benefited greatly from a new understanding of the plasticity of the brain, and from technological advances in recording movement and brain activity.

The importance of N. Bernstein

The legacy from the neuroembryologists, through Gesell and McGraw, was that movement was a direct read-out of the maturational status of the nervous system. The reverse was scarcely considered—that the developmental course of the nervous system may be moulded by the nature of the body and how it moves. Bernstein’s (1967) seminal insight was to pose the control issue differently. He started with the body, which, he noted, had hundreds of bones and joints and millions of muscle fibres. Yet every movement is a coherent, coordinated event. How can the brain accomplish this feat of coordination, given so many possible combinations, or degrees of freedom? The answer, according to Bernstein, was that movements were organised in synergies, that is, a functional linking together of muscles into ensembles that worked together. What the brain recruited, according to Bernstein, was not individual muscles, but an appropriate pattern to accomplish a functional task. This vastly simplified the control problem. Indeed, Bernstein showed that movement was function specific and not muscle specific: his classic example is that you can sign your name using a pen on paper or using a broomstick on a blackboard, but the signature remains the same.

Moreover, as the motor system is assembled for functional action, it actually exploits the mechanical properties of the limbs and body. For example, limbs have spring-like properties because of the elastic qualities of the muscles and the anatomical configuration of the joints. When an ordinary spring is stretched and let go, it oscillates in a regular trajectory. The movement pattern need not be configured explicitly because it arises from the natural properties of the spring. Likewise, many aspects of human movements need not be detailed in the nervous system because they arise by themselves from the natural properties of the body. One good example is walking: as people step on one leg and then shift their weight forward over it, the back leg is stretched and stores energy, like a spring. As that leg then swings forward, it uses little active muscle contraction, but rather relies on the potential energy gained by stretching the muscles.

In his writing on the development of movement, Bernstein turned the old theories on their heads. It was not, he claimed, so much the nervous system instructing the muscles, as the dynamics of the movement instructing the nervous system. Children must learn the biodynamics of their bodies, the changing forces that produce and accompany each movement in each situation. To learn to walk, for instance, infants must deal with the complex interactions between the movements of the legs, the centre of gravity of the body, and the support surface. These cannot be instructed beforehand, but must be individually assembled through experience. Eventually, infants learn not just to control their movements, but to make them efficient by exploiting their biomechanics, that is, using what the system can provide “for free”.

The impact of Bernstein on the study of motor development was to shift the focus from thinking exclusively of the central nervous system as the sole contributor to the emergence of new skills to considering the ...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Figures
• Tables
• Contributors
• Preface
• 1 Motor development as foundation and future of developmental psychology
• 2 The early experience assumption: Past, present, and future
• 3 Behavioural genetics in the 21st century
• 4 Nutritional deficiencies as a biological context for development
• 5 Prospects for research on the quality of pre-school experience
• 6 Development of children’s knowledge about the mental world
• 7 Domain-specific constraints of conceptual development
• 8 Research on memory development: Past and present
• 9 Mindreading, emotion understanding, and relationships
• 10 Lifespan personality development: Individual differences among goal-oriented agents and developmental outcome
• 11 Perspectives on gender development
• 12 Agency in development
• 13 The development of aggressive behaviour during childhood
• 14 Cross-cultural views on human development in the third millennium
• 15 Transitions in adolescent research
• 16 The impact of longitudinal studies on understanding development from young adulthood to old age
• 17 Growing points in developmental science: A summing up