The article by Yang et al (Reference Yang, Raine and Lencz2005) is provocative, thoughtful and intriguing and provided much food for thought. Participants were divided into three groups: liars, normal controls and antisocial controls. Half of those in the liars group were malingerers and the others displayed conning/manipulative behaviour on the Psychopathy Checklist - Revised (PCL-R), deceitfulness criteria for DSM-IV antisocial personality disorders or pathological lying as defined in the PCL-R. Yang et al referred to pathological liars specifically in the title of their paper but we are concerned that the definition of liars was so broad and wondered whether the article would not have been better entitled ‘Prefrontal white matter in liars’. The authors included individuals with different lying characteristics in a group of pathological liars and this is problematic.

Our recent review (Reference Dike, Baranoski and GriffithDike et al, 2005) showed that the term ‘pathological lying’ has been used differently in the literature from how it was used by Yang et al. Pathological lying is distinct from malingering or the other forms of lying exhibited by those included by Yang et al in the liars group. We defined pathological lying as ‘falsification entirely disproportionate to any discernible end in view, may be extensive and very complicated, and may manifest over a period of years or even a lifetime’. Pathological lying is a repetitive pattern of lying for which an external reason (such as financial gain) often appears absent, and the psychological basis is often unclear. This definition has not been accepted by the psychiatric community but summarises the elements of pathological lying. Interestingly, we found that pathological lying can also be found among successful individuals without a history of criminal behaviour.

We commend Yang et al for investigating the neurobiological basis of lying. Whether the prefrontal white matter changes indicate a causal relationship with lying or just an association is unknown. However, pathological lying per se was not specifically investigated, as suggested.