Psychopathy is a personality disorder associated with severe emotional and interpersonal consequences and persistent antisocial behavior. Neurobiological models of psychopathy emphasize impairments in emotional processing, attention, and integration of information across large-scale neural networks in the brain. One of the largest integrative hubs in the brain is the corpus callosum (CC) – a large white matter structure that connects the two cerebral hemispheres.

The current study examines CC volume, measured via Freesurfer parcellation, in a large sample (n = 495) of incarcerated men who were assessed for psychopathic traits using the Hare Psychopathy Checklist-Revised (PCL-R).

Psychopathy was associated with reduced volume across all five sub-regions of the CC. These relationships were primarily driven by the affective/interpersonal elements of psychopathy (PCL-R Factor 1), as no significant associations were found between the CC and the lifestyle/antisocial traits of psychopathy. The observed effects were not attributable to differences in substance use severity, age, IQ, or total brain volume.

These findings align with suggestions that core psychopathic traits may be fostered by reduced integrative capacity across large-scale networks in the brain.

The occurrence of a significant relationship between psychopathic traits and intelligence is still open to debate. Most of the relevant information has been obtained from crystallized IQ tests or on psychopathic male offenders. In this study we hypothesized a negative correlation between psychopathic traits and fluid intelligence on a sample of criminal female in-patients.

We carried out a correlational study on a selected sample of 56 criminal female offenders. Variables that were measured include the Hare Psychopathy Checklist Revised (PCL-R) total score (and, separately, the scores from its four subscales: Interpersonal, Affective, Lifestyle and Antisocial) and fluid IQ measured by Raven's Progressive Matrices (RPM).

Pearson's correlation between RPM IQ and total PCL-R score was negative (r54 = − 0.55, p < 0.001); women with greater psychopathy traits (total PCL-R score) had lower IQ scores. Negative correlations were also found between IQ and the four PCL-R subscales, Interpersonal, Affective, Lifestyle and Antisocial (r54 = − 0.35, p < 0.01, r54 = − 0.52, p < 0.001, r54 = − 0.53, p < 0.001, and r54 = − 0.49, p < 0.001 respectively).

The results indicate a general negative relationship between PCL-R and IQ, equally distributed across the four subcomponents of the psychopathic trait, and support the view that unsuccessful psychopathic women have poor planning and are unable to foresee and represent future consequences of their actions.