In fiction and non-fiction, comics, television shows and films, the preponderance of people exhibiting psychopathy nearly rivals that of superheroes. And despite no end of volumes written by journalists, friends, relatives, media-darling scientists and people claiming to be psychopaths themselves, it is rare to find an accessible book on the subject by a researcher who is an acknowledged leader in the field. Kent Kiehl is the exception to the rule.

In spite of a title that doesn¡¯t entirely capture the complexity of the topic Kiehl addresses so well, the book¡¯s examination of electrophysiology and the use of magnetic resonance imaging (MRI) in studying psychopathy attest to the author¡¯s expertise as a neuroscientist. Interestingly, its beginning is strongly reminiscent of Without Conscience: The Disturbing World of the Psychopaths Among Us, a 1993 work by Robert Hare, an eminent researcher and Kiehl¡¯s PhD mentor. Both texts begin with anecdotes drawn from the authors¡¯ time working in maximum security prisons where psychopaths challenged and threatened them, and include descriptions of the big red button to be pressed (irresistibly but futilely) in case of emergency. As a young scholar, Without Conscience inspired a passion in me to understand the developmental origins of psychopathy. Two decades later, Kiehl¡¯s book looks certain to inspire a new generation of budding researchers.

Psychopathy typically leads, if not to murderous behaviour, then to a parasitic penchant to use people for personal gain

Particularly notable in Kiehl¡¯s work is his use, unique to his lab, of a mobile MRI unit that allows him to perform brain scans on incarcerated research subjects for signs of psychopathy. In The Psychopath Whisperer, he offers an anecdote about the genesis of that innovation: he was once almost run off the road by an articulated lorry carrying such a unit. That brush with death suggested a practical way to solve the problem of the relatively low number of research participants within prison populations: bring the MRI to the prisoners, rather than the other way round.

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As Kiehl acknowledges, the media and public tend to confuse illegal behaviour ¨C and, in particular, exceptionally horrifying acts of violence ¨C with psychopathy. In addressing the difference between the popular and scientific use of the terminology, The Psychopath Whisperer considers criminals with and without psychopathy. Near the beginning of the book, Kiehl focuses on one of his subjects, Mike, to show how criminal non-psychopaths such as he differ from criminal psychopaths: although Mike had a long history of criminal behaviour and had engaged in more than one bad act, he experienced guilt. Kiehl also considers the historical cases of two men who committed terrible crimes: John Wilkes Booth, who shot president Abraham Lincoln, and Charles Guiteau, who killed president James Garfield. He uses file reviews to attempt to diagnose psychopathy in the two using the Psychopathy Checklist created by his mentor Hare ¨C a strikingly clever and effective way to show how two people who committed apparently similar acts can differ on psychopathy. (The only drawback in this instance is that Kiehl is comparing people who differed not only in their capacity for remorse, empathy and emotion but also in lifelong behaviours and motivation.)

Heated debates rage in and out of the disciplinary journals about the essential features someone must show to be classified as a psychopath, which Kiehl acknowledges is a scientific classification and not one yet recognised in the American Psychiatric Association¡¯s periodically updated Diagnostic and Statistical Manual of Mental Disorders (DSM). The question remains whether one must be a criminal to be a psychopath, and this argument, notes Kiehl, has been going on for a century. (And, indeed, some of the historical issues around the DSM classification of antisocial personality disorder make one seriously consider having a squabble with behaviourists.) Early descriptions of psychopathy were virtually devoid of references to criminal or antisocial behaviour, but when diagnostic classifications were revised for the DSM-III in 1980, psychiatrists believed that behaviours were easier to assess than the more nebulous personality traits of emotional and empathy deficits. Thus, Kiehl says, antisocial personality disorder was born ¨C somewhat unsatisfyingly, as diagnosticians and researchers saw the inherent heterogeneity in both this disorder and conduct disorder in children. Since then, researchers have been slogging away to add the affective deficits that were left out of the criteria.

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In his book¡¯s chapters on neuroscience, Kiehl considers psychopathy as a disorder of emotion, which he connects with findings drawing on brain imaging and behavioural work. His research connects these emotional deficits more clearly to the brain areas involved in emotion and empathy. Research on children with callous-unemotional traits, which Kiehl links with adult psychopathy, shows these same brain areas to be involved. His description of callous-unemotional traits, and their inclusion in the DSM-5 in 2013, is thorough and insightful. At times, Kiehl seems to argue that the presence of adolescent brain functioning deficits related to callous-unemotional traits suggests that these adolescents were born with such brain deficits. But, in an illuminating comparison, he acknowledges that brain abnormalities seen in adults with psychopathy could be due to environmental influences, similar to the atrophy of an unused muscle. Arguably the same might be said of adolescents with these traits, given the early abuse that juvenile offenders typically report. Importantly, Kiehl supports the idea of the potential for the adolescent brain to be reorganised ¨C negatively or positively ¨C because the typical developmental changes across the brain throughout development have yet to be systematically mapped.

People with psychopathy historically have been assumed to be resistant to treatment. Kiehl, however, points to a ray of hope in a chapter on an exciting and relatively new treatment facility for young offenders, the Mendota Juvenile Treatment Center in Wisconsin. The delight he takes in its development and success is every bit as infectious as his inveterate-foodie asides, throughout the book, about meals he¡¯s enjoyed. The crux of his argument about treatment is that it has only recently been designed to directly target modifying behaviours in people with psychopathic traits using methods to which they are most likely to respond. He enthusiastically espouses programmes such as this one, that target young people who are arguably more amenable to treatment efforts, even young offenders with callous-unemotional traits and the hardest behaviours to manage. More funding, he argues, should be given to such programmes ¨C and who could disagree?

Linked to the debate about the inclusion of criminal behaviour in classifications of psychopathy, there exists the unfounded idea that people with psychopathy make good citizens on occasion and are generally an asset to society ¨C the Dexter hypothesis, if you will. But Kiehl insists, with decades of research to support him, that psychopathy is a disorder, both a moral and an emotional one. He emphatically states that such traits will pervade across one¡¯s life, across relationships and across contexts. Psychopathy typically leads, if not to murderous behaviour, then to a parasitic penchant to use other people for personal gain, leaving many of the victims destitute and emotionally overwrought. It is not a transient comportment, he explains, or a momentary, fleeting lack of fear under threat of danger. And, although one of the psychopaths Kiehl meets provocatively declares that the Psychopathy Checklist should be renamed the Superman Checklist, people with psychopathy are rarely heroic. In The Psychopath Whisperer, Kiehl offers an insightful and memorable look into the troubled minds of people with psychopathy and invites us to explore further.