Institute of Behavioral Sciences, Semmelweis University, Budapest, Hungary
Department of Neuroradiology, National Institute of Psychiatry and Neurology, Budapest, Hungary
Cognitive Science Research Group, HAS-Budapest Technical University, Hungarian Academy of Sciences, Budapest, Hungary
*Correspondence: Klára Horváth, Institute of Behavioural Sciences, Semmelweis Univesity, Budapest, Hungary.

Basic personality factors are sets of measurable dimensions providing simple description of personality in its entirety. Even though there is a considerable agreement on five factor models which could best fit the above description, the exact contents of the factors are disputed. Eysenck and Zuckerman claim that associations with biological trait markers are necessary as an additional criterion. Such trait markers could be the volumes of various brain structures in personality associated brain areas. Our aim is to support Zuckerman’s theory of Sociability as being a basic factor by using MRI-based volumetric measures as biological trait markers. As far as we know the neuroanatomic correlates of Sociability have not been studied yet. There are several studies which examined the NEO-PI-R Extraversion, but the results are inconsistent. We assume that this inconsistence is caused by the combination of other factors (Activity, Sensation Seeking, Impulsivity).

Sociability was assessed by the Hungarian version of ZKPQ. The volumes of brain structures were measured by analysing MRI scans with the HAMMER software package. Product-moment correlation coefficients were computed from data of 25 healthy participants.

Significant positive correlations were found between Sociability scores and the volumes of several structures including the left and right insula, temporal lobe, the right frontal lobe and the basal ganglia for men. Although we had only 7 women in our sample, Sociability correlated significantly with the neocortex and left insula. Our findings may be interpreted as an extension of the social brain theory of Dunbar from the interspecies level to the interindividual one, providing an explanation for the fact that primates have larger brains relative to their body sizes. Increased and more complex social life could be associated with increased brain volumes at both the interspecies and the interindividual level.