The parasite Toxoplasma needs to get from its intermediate hosts, e.g. rodents, to its definitive hosts, cats, by predation. To increase the probability of this occurrence, Toxoplasma manipulates the behavior of its hosts, for example, by the demethylation of promoters of certain genes in the host's amygdala. After this modification, the stimuli that normally activate fear-related circuits, e.g., the smell of a cat in mice, or smell of leopards in chimpanzees, start to additionally co-activate sexual arousal-related circuits in the infected animals. In humans, the increased attraction to masochistic sexual practices was recently observed in a study performed on 36,564 subjects. Here I show that lower rather than higher attraction to sexual masochism and submissiveness among infected subjects is detected if simple univariate tests instead of multivariate tests are applied to the same data. I show and discuss that when analyzing multiple effects of complex stimuli on complex biological systems we need to use multivariate techniques and very large data sets. We must also accept the fact that any single factor usually explains only a small fraction of variability in the focal variable.

Division of Biology Faculty of Science Charles University Prague Czech Republic

National Institute of Mental Health Klecany Czechia

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Flegr J, Preiss M, Klose J, Havlíček J, Vitáková M, Kodym P. Decreased level of psychobiological factor novelty seeking and lower intelligence in men latently infected with the protozoan parasite Toxoplasma gondii. Dopamine, a missing link between schizophrenia and toxoplasmosis? Biol Psychol 2003; 63:253-68; PMID:12853170; http://dx.doi.org/10.1016/S0301-0511(03)00075-9 PubMed DOI

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Skallová A, Kodym P, Frynta D, Flegr J. The role of dopamine in Toxoplasma-induced behavioural alterations in mice: an ethological and ethopharmacological study. Parasitology 2006; 133:525-35; PMID:16882355; http://dx.doi.org/10.1017/S0031182006000886 PubMed DOI

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Special Issue: Re-assessing host manipulation in Toxoplasma: the underexplored role of sexual transmission - evidence, mechanisms, implications

Thirty years of studying latent toxoplasmosis: behavioural, physiological, and health insights