Big Five

oxoplasmosis is associated with speci fi c differences in the personality of infected subjects relative to non-infected subjects. These differences are usually cons idered to be a side effect of the manipulative activity of the parasite aimed to increase the probability of its transmission from the intermediate host to the de fi nitive host by predation. The personality of infected s ubjects was studied mostly using the Cattell ’ s questionnaire. However, this questionnaire is now considered outdated and has been mostly substituted with the Neuroticism – Extraversion – Openness Personality Inventory — Revised (NEO-PI-R) questionnaire in clinical practice. Here, we searched for the as- sociation between toxoplasmosis and the personality by screening a population of students with the NEO-PI-R question- naire. We found that Toxoplasma-infected male and female students had signi fi cantly higher extraversion and lower conscientiousness. The conscientiousness negatively correlated with the length of infection in men, which suggested that the toxoplasmosis associated differences were more probably the result of slow cumulative changes induced by latent toxoplasmosis, rather than transient side effect of acute Toxoplasma infection. The existence of this correlation also sup- ported (but of course not proved) the hypothesis that Toxoplasma infection in fl uenced the personality, rather than the hypothesis that the personality in fl uenced the probability of the infection.