Darwinian shrinks

Given that the mind is the product of the brain, it struck Henry Plotkin as decidedly odd that the academic discipline of psychology had rightly seen itself as one of the biological sciences and yet had divorced itself from evolutionary theory. In his new book, he set out to understand the historical factors that led to this regrettable separation.

This state of affairs was particularly odd because psychology has at times striven virtually to be a branch of physiology, with its emphasis on experimentation, proximate causes and reductionism to the neural level; yet unlike physiology, it lost sight of the ecological functions of its subject matter (behaviour). Of course, there are some well-known exceptions to this, such as John Bowlby's ethological theory of attachment, but Plotkin's excellent book traces the regrettable history of psychology as a non-Darwinian science and attempts to reinstate it as a Darwinian one.

Plotkin blames several factors for the drift away from an evolutionary framework. First, there is British empiricism (eg, in the 18th century and earlier, John Locke and David Hume claimed that there is no innate knowledge, only associations between sensations). Second, the German psychophysics tradition (eg, in the 19th and early 20th centuries, the work of Gustav Fechner, Wilhelm Wundt and Hermann Helmholtz, with its emphasis on measurement, almost for its own sake). Plotkin highlights how William James, working in Harvard in the early part of this century, brought psychology back into contact with Darwinian ideas, through functionalism and notions of adaptation, but that such ideas were lost sight of as US psychology drifted into behaviourism.

Two other subsequent attempts to bring Darwinian thinking back into psychology also fell on troubled times: Francis Galton's nativist approach soon came to be associated with the eugenics movement, which was understandably morally repugnant, and instinct theory came to be almost laughable as no one could agree on what was an instinct or how many instincts there were. Indeed, psychology had to await the arrival of ethology (and a Nobel prize to its founding fathers, Konrad Lorenz, Karl von Frisch and Nikolaas Tinbergen), as well as Noam Chomsky's devastating critique of Skinnerian behaviourism, before Darwinian ideas could have a chance to re-enter the field.

Meantime, Plotkin notes that psychology missed certain opportunities, and in fact the revolution occurred in a neighbouring discipline instead: sociobiology. Admittedly, sociobiology also fell into disrepute for a short time, when all of behaviour was being reduced to Darwinian factors, but as Plotkin shows, by the close of the 20th century, a more balanced form of Darwinian thinking is developing in psychology.

Plotkin's book is in part a historical account, and very readable for that. It then surveys contemporary "evolutionary psychology", focusing on language as a particularly developed example, and other cognitive domains such as folk psychology (our everyday understanding of social causation) and folk physics (our everyday understanding of physical causation). These chapters review many empirical studies and theoretical arguments, and Plotkin's elegant style shines through.

I enjoyed this book, not only because it takes a bird's-eye view of the discipline of psychology as it spans several centuries, but also because it helps the reader to situate the current interest in evolutionary psychology. The book requires a fair bit of background knowledge to move at Plotkin's pace; it is more for a final-year undergraduate or above, rather than an introductory text.

Simon Baron-Cohen is lecturer in experimental psychology and psychiatry, University of Cambridge.