Most people are repelled and intrigued by the images of cold-blooded, conscienceless murders that increasingly populate our movies, television programmes and newspaper headlines. With their flagrant criminal violation of society's rules, serial killers like Ted Bundy and John Wayne Gacy are among the most dramatic examples of the psychopath. Individuals with this personality disorder are fully aware of the consequences of their actions and know the difference between right and wrong, yet they are terrifyingly self-centred, remorseless and unable to care about the feelings of others. Perhaps...