Higher Extraversion and Lower Conscientiousness in Humans Infected with Toxoplasma

Abstract

Toxoplasmosis is associated with specific differences in the personality of infected subjects relative to non-infected subjects. These differences are usually considered 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 definitive host by predation. The personality of infected subjects 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 However, this questionnaire is now considered outdated and has been mostly substituted with the Neuroticism-Extraversion-Openness Personality Inventory-Revised (NEO-PI-R) questionnaire in clinical practice.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 association between toxoplasmosis and the personality by screening a population of students with the NEO-PI-R questionnaire. We found that Toxoplasma-infected male and female students had significantly 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 supported (but of course not proved) the hypothesis that Toxoplasma infection influenced the personality, rather than the hypothesis that the personality influenced the probability of the infection.

Toxoplasmosis-Associated Difference in Intelligence and Personality in Men Depends on Their Rhesus Blood Group but Not ABO Blood Group

“…About 10 published studies have demonstrated associations of toxoplasmosis with human personality traits mostly using Cattell's 16PF and Cloninger's TCI questionnaires; for review, see [26], [43], [44]. Only one study, showing positive association of toxoplasmosis with extroversion and its negative association with conscientiousness, used the NEO-PI-R questionnaire [45]. A correlation study has also shown that the difference in the prevalence of latent toxoplasmosis between the general populations of particular countries can explain a significant portion of the variance in aggregate neuroticism among populations [46].…”

Rhesus Factor Modulation of Effects of Smoking and Age on Psychomotor Performance, Intelligence, Personality Profile, and Health in Czech Soldiers

“…In many countries in Europe, South and Central America, and Africa, more than 50% of the population acquire this parasitic infection during their life [9], [10]. Infected subjects who carry the dormant stages of this protozoan parasite for the rest of life differ from the uninfected ones in the personality profile [11], reaction time [12], secondary sex ratio [13], olfactory preferences [14], risk of schizophrenia [15], [16], brain cancer [17], traffic accidents [18], and suicides [19] [20]. The amount of change usually increases with the duration of toxoplasmosis and most changes were also observed in artificially infected laboratory animals.…”

Influence of latentToxoplasmainfection on human personality, physiology and morphology: pros and cons of theToxoplasma–human model in studying the manipulation hypothesis

“…This is an important obstacle to the study of the causal relationship between Toxoplasma infection and various toxoplasmosis-associated traits. For example, the lower NEO PI-R conscientiousness in infected subjects (Lindová et al, 2012) could be an effect of the infection or it may be that there is a higher probability of infection in persons with lower conscientiousness who may have a lower tendency to adhere to hygienic standards. In some cases, the causality direction is quite obvious.…”

“…Some studies also suggest that infected subjects have higher scores on Cloninger's ST -self-transcendence Skallová et al, 2005). The NEO-PI-R questionnaire showed more extraversion in infected subjects, both men and women, and less conscientiousness in comparison with Toxoplasma-free subjects (Lindová et al, 2012). On the basis of predictions of the manipulation theory and introspection of the Toxoplasma-infected author, a special questionnaire called Toxo94 was constructed (Flegr, 2010b).…”