How Intelligence Happens is a fantastic popular science book about how and where in the brain intelligence occurs and what exactly intelligence is from a psychological perspective. After an entertaining preamble into the basics of learning in the animal kingdom, one classical, profound fact is centred on: that people who do well on one mental task tend to do well on others. This one result, discovered a century ago, Duncan argues, reveals so much about intelligence and cognition in general. Duncan himself was responsible for linking this result with specific brain regions, and much of the rest of the book is concerned with the brain-scanning and monkey single neuron recording studies, primarily in the prefrontal cortex, which reveal the neural signature of intelligence. What exactly is this marker? Duncan argues, partly via results from artificial intelligence, partly from studies in people with low IQ and partly in patients with prefrontal damage, that the key psychological process that makes us intelligent is the ability to chain together a heirarchy of mental programs and sub-programs in order to achieve the complex goals we set ourselves. Therefore, intelligence, as supported by prefrontal (and parietal) regions, is about organising our behaviour in a logical, goal-directed way. Perhaps we learn to generalise these programs to a sufficient degree that they mutate into abstract results, and we gain wisdom and not just intelligence.

Many current popular science books suffer from being written not by scientists embedded in the field but journalists, and thus are filled with inaccuracies or only a superficial understanding of the topic. Others are filled with unsupported hyperbolae. How Intelligent Happens is in some ways the antithesis of those books, since John Duncan is a world leader in the neuroscience of intelligence, and his scholarly knowledge and authority oozes from every page, strongly enhanced by his honesty about the strength - or weakness - of certain results, even from his own lab. You constantly feel that you are hearing from a very bright scientist at the cutting edge of the topic.

The style, especially at the start, is extremely accomplished, rather literary, while for the meat of the book is still always sharp and accurate, to match his thinking. There are regular anecdotes, some very funny, and a fun smattering of references from fiction and television to illustrate his arguments.

This is a marvellously clear, highly focused account of what intelligence is from the point of view of mind and brain - it achieves this goal brilliantly and is one of the best popular science books I've read in a long time. ( )