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A Dynamic Systems Approach to the Development of Cognition and
Action
David J. Lewkowicz and Robert Lickliter.
Journal of Cognitive Neuroscience (Fall 1995): pp512(3)
Life, said the English novelist Samuel Butler, is like giving a concert on the violin while
learning to play the instrument. Butler's insight-that there are no distinct training and
performance modes in development - succinctly captures the activity-dependent nature of
the developmental process. For example, imagine a baby learning to walk. Although
babies spend a great deal of time failing down, getting up, and falling down again, as far
as some parents are concerned, their child's walking seems to magically appear de novo
one day. Other parents, however, do appreciate the importance of their baby's ups and
downs and believe the old saying that practice makes perfect" in the emergence of
walking. Butler's insight, however, suggests a third perspective on the emergence of such
novel behavior: namely, that there are no practice modes in development-all activity
counts in selecting, constructing, and maintaining behavioral outcomes. This fundamental
role that self-generated activity plays in the development of all behavioral functions,
ranging from motor behavior to perception, cognition, and social behavior, is a central
theme of the dynamic systems approach that is masterfully explicated in the recent book
by Esther Thelen and Linda B. Smith. In this book the authors (both developmental
psychologists) apply the principles of nonlinear dynamic systems to motor, perceptual,
and cognitive development and the result is a remarkable synthesis and advancement of
developmental science. Indeed, it would not be an exaggeration to say that this volume
offers a revolutionary perspective on the development of cognition and action.
According to Thelen and Smith the primary thrust of development is the generation of
novel structure and behavior. In their attempts to explain this complex process, Thelen
and Smith eschew the classic dualisms of structure vs. function, nature vs. nurture, brain
vs. behavior, perception vs. cognition, mind vs. body, competence vs. performance, and
learning vs. development. Their rejection of dualistic thinking results in a radical
departure from current cognitive theory and provides a view of development in which
stability and change are accommodated under a single theoretical umbrella. This
umbrella, of course, is dynamic systems theory, an approach that is doubtlessly familiar
to many of the readers of this journal. What makes this book different from other books
on the topic of dynamic systems, and more useful than many in this genre, is both its
breadth and its explicit focus on the developmental processes underlying the emergence
of motor, perceptual, and cognitive functions. Indeed, we believe Thelen and Smith's
book is unique in this area in that it provides multiple examples of the successful
application of the dynamic systems approach to the study of human development as well
as a methodological agenda for the generation of new research programs.
Thelen and Smith begin their book by discussing the shortcomings of many of the major
theoretical systems associated with the study of human development (e.g., maturationist,
neurological, rationalist-nativist, and information processing) and note that all of these
approaches have a common teleological core that implicitly presumes an "end-state"
before the developmental process even begins. The authors then go on to reject simple cause-and-effect models that rely on predeterminism, linearity, and reductionism. In their
place, they offer a comprehensive approach to the development of behavior that focuses
on the processes underlying change in dynamic, self-organizing systems. These systems
have a history, can create novelty out of contextual and organismic conditions, and do not
have an "end-state" coded anywhere. The early chapters of the book are organized to
showcase the authors' own research programs on early motor (Thelen) and cognitive
(Smith) development to illustrate the explanatory power of this approach for complex
behavioral phenomena. In these chapters the authors also utilize the power of their
approach to show how previous interpretations of findings in these research areas are
misguided in relying on concepts of innate programs or innate knowledge structures.
In subsequent chapters Thelen and Smith address the relation between morphology,
neural processes, and behavior in promoting developmental change. In relating these
three, the authors rely heavily on N. A. Bernstein's (1967) concept of indeterminacy and
Gerald Edelman's (1987) concepts of selection and reentry the interrelating of several or
many simultaneous perceptual and motor representations) to provide the means by which
novel neural and behavioral structures and functions may be "soft-assembled" in real and
developmental time. Of particular interest to the readers of this journal is the authors'
argument that the dynamics of behavioral phenomena and the known dynamics of neural
phenomena should be consistent with one another. Most importantly, Thelen and Smith
argue that a reductionistic approach that resorts to interpretations based solely on neural
factors leads to infinite regress in our explanations of the process of the emergence of
novel structure and behavior. In their dynamic systems approach, the neural aspects of
human functioning are part-and-parcel of the individual's entire developmental system.
No single element or level in this system necessarily has causal primacy or privilege.
Indeed, Thelen and Smith's approach to development virtually requires that equal status
be given to all contributing factors at all levels of analysis.
A central question for students of perceptual and cognitive development is how
perceptual categories, which are the foundation of human cognition and action, emerge
during development. What are the processes and mechanisms that allow meaning to be
assigned to the multiple and continuous sensations of everyday life? Thelen and Smith
devote a major section of the book to a discussion of this question and propose that the
answer must lie in (1) the recognition of the fundamental unity of perception and action
and (2) the critical importance of the temporal association of multimodal information in
creating the link between the mind and the world. In their active exploration of the world,
infants receive massive amounts of time-locked, multimodal sensations. The authors
argue that infants discover action and object categories through the cross-correlation of
these multimodal experiences. In their own words, "what infants know and how they act
are selected continuously and dynamically from what they encounter and how they act.
Sensory integration is the primitive, not the derived state, and knowledge is limited not
primarily by deficits in storage but in the ability to adequately sample and thus categorize
the world" (p. 21 1). This position obviously challenges much contemporary work in the
field of cognitive development and will likely engender controversy among students of
cognition. In the remaining chapters of the book Thelen and Smith discuss and explain
developmental phenomena as diverse as memory, traversing slopes, word knowledge,
reaching, and the A-not-B error within the dynamic systems framework. For example,
Thelen and Smith demonstrate the value of dynamic systems principles in explaining the
development of reaching in human infants. They show through the detailed longitudinal
study of individual infants' performance how different babies arrive at very different
solutions to the common problem of retrieving an object. Through detailed examination
of the day-to-day variations in arm movements, the authors convincingly demonstrate the
unique developmental pathways that different infants utilize in their eventual solution to
the problem of reaching. By doing so, Thelen and Smith elucidate the distinctive,
context-dependent, and self-organized nature of development. In their own words, the
"solutions were discovered in relation to their own situations, carved out of their
individual landscapes, and not prefigured by a synergy known ahead by the brain or the
genes" (p. 260).
Thelen and Smith conclude the book with a considered look at the "hard problems"
facing contemporary developmental science. In their opinion, one of the key unresolved
areas is the traditionally thorny issue of value and motivation. In their discussion they
resurrect the important but often overlooked contributions of Kurt Lewin, who
recognized the significance of a systems approach to behavior over half a century ago. In
particular, Lewin focused on the central role of value and motivation in directing
developmental change. Similarly, the concept of value is also very important to Thelen
and Smith's dynamic systems theory because it provides a primary mechanism by which
perceptual categorization is achieved. Value provides the motivational impetus for the
organism to seek certain forms of stimulation and not others. Thus, very early in
development, infants might be biased to seek contact or warmth, prefer light over dark,
seek objects that can be sucked or touched, etc. Once objects or events that are preferred
are encountered, different properties of these objects or events can then be differentiated
through recurrent experience. According to Thelen and Smith, infants come into the
world with a set of values or hedonic valences and the authors suggest that such values
are somehow epigenetically acquired. What the authors do not offer, however, is a
mechanism by which epigenetic forces confer positive or negative valence on particular
forms of stimulation.
One such possible mechanism was proposed decades ago by the comparative
psychologist T. C. Schneirla (1959). After revie
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