At the time of writing this review, one of the hot films was The Social Network, a dramatisation of the founding of Facebook by the Harvard student Mark Zuckerberg. Jesse Eisenberg plays Zuckerberg as a borderline sociopath who lacks human empathy, yet is colossally endowed with the sort of genius that made the invention of Facebook possible. Had I gone to the movie with Simon Baron-Cohen, director of Cambridge’s Autism Research Centre and author of this important and ground-breaking book, I am sure he would have sat beside me chuckling with delight as he recognised in Eisenberg’s performance the perfect outline of one of the personality types he describes. A person who appears to me to be just another rude and impatient nerd is, to him, a perfect example of someone who is zero-positive on his empathy bell curve. He defines empathy as our ‘ability to identify what someone else is thinking or feeling, and to respond to their thoughts and feelings with an appropriate emotion’. Those who are at the zero end of the curve are neurologically incapable of empathic response, but they come in two types, positive and negative, and there is a world of moral difference between them. People who are zero-positive on the empathy continuum have autism spectrum condition, but the very condition that compromises their capacity for empathy also endows them with a powerful systemising facility that has been of immense benefit to humanity. Zero-positives may have to make learned adjustments in order to interact with people, but Baron-Cohen wants us to understand and even celebrate what makes them tick neurologically.

But what about the zero-negatives on his empathy spectrum, the borderline personalities and psychopaths? This is where we shiver with apprehension, especially over the latter. The good professor won’t mind the shiver, but he also wants to propel us into greater understanding. What prompted him to the research