Developing Intelligence

In a few places throughout the second edition of his landmark book, Mark Johnson suggests that the field of developmental cognitive neuroscience has matured from infancy to toddlerhood. This book, then, is a sort of biography, from the field’s theoretical ancestry in 17th century debates between “vitalists” and “preformationalists” to current (and in some ways similar) debates between nativists and empiricists. In between, Johnson expertly covers everything from prenatal cortical differentiation to developmental change in the distributions of various neuromodulators, to the development of simple oculomotor function, to prefrontal processes supporting object permanence. Johnson draws from genetic, neuroimaging and behavioral research, postmortem analysis of developing human brains, various neural network models, and even in vitro experiments with a variety of brain tissues.

Along the way, Johnson analyzes how each aspect of functional brain development can be accounted for by three basic views. One, which he terms the “maturational” view, supposes that brain development is largely pre-determined by genes, and further that these neural changes can be directly related to cognitive change. A second contrasting view, which Johnson terms the “skill learning” view, supposes that the mechanisms guiding cognitive development are similar or identical to those guiding skill acquisition in adults. Finally, a third view – which Johnson calls “interactive specialization” – represents a fusion of the previous two perspectives. According to this perspective, broad patterns of connectivity are innately specified, but the ultimate computations supported by brain regions rely on an interaction between maturational processes and neural activity resulting from experience throughout a variety of neural networks.

Although this tripartite framework necessarily simplifies the theoretical debates surrounding each topic, it has many advantages as a rhetorical device. For example, the tone of the book is noticeably more conversational than the didactic quality of other textbooks which avoid controversial issues altogether (or perhaps worse, present just a single interpretation as fact). Secondly, this framework gives the book a strong coherence, despite the wide variety of methodologies, levels of analysis, and topics reviewed throughout. This leads to a polished work equally suited to the graduate classroom as to the libraries of interested laypeople.

In general, the book is skewed towards infancy; accordingly, the visual system is covered in detail while much less space is allocated to the development of higher-level cognition and explicit memory. On the other hand, Johnson’s treatment of early social cognition is particularly impressive and wide-ranging, covering topics from parental “imprinting” in chicks to the development of face recognition, gaze-tracking, and ultimately theory of mind. Johnson notes that an introductory text such as this is necessarily selective, but the analytical depth of what is covered more compensates for this in my view. Furthermore, Johnson recommends additional readings for nearly every major point, which provides a great starting point for readers interested in learning more about a specific topic.

This book is likely to be enjoyed by dedicated laypeople, new graduate students, and research professionals alike, thanks to Johnson’s knack for explaining even complex topics at an easily-understood level of detail. Unlike many popular science books, this more academic text steers clear of over-generalization, instead carefully explaining the evidence used to support each argument. Johnson’s Developmental Cognitive Neuroscience comes highly recommended as an introductory textbook to this exciting new field.