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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Berdoy M, Webster JP, Macdonald DW. Fatal attraction in rats infected with PubMed DOI PMC

Flegr J, Lenochová P, Hodný Z, Vondrová M. Fatal attraction phenomenon in humans: cat odour attractiveness increased for PubMed DOI PMC

Dass SAH, Vyas A. PubMed DOI

Flegr J, Markos A. Masterpiece of epigenetic engineering - how PubMed DOI

Poirotte C, Kappeler PM, Ngoubangoye B, Bourgeois S, Moussodji M, Charpentier MJE. Morbid attraction to leopard urine in PubMed DOI

Vyas A, Kim SK, Giacomini N, Boothroyd JC, Sapolsky RM. Behavioral changes induced by PubMed DOI PMC

Jozífkova E, Bartoš L, Flegr J. Evolutional background of dominance/submissivity in sex and bondage: the two strategies? Neuroendocrinol Lett 2012; 33:636-642; PMID:23160222 PubMed

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Flegr J, Kuba R. The relation of DOI

Flegr J, Lindová J, Pivoňková V, Havlíček J. Brief Communication: Latent toxoplasmosis and salivary testosterone concentration-important confounding factors in second to fourth digit ratio studies. Am J Phys Anthropol 2008; 137:479-84; PMID:18615572; http://dx.doi.org/ 10.1002/ajpa.20888 PubMed DOI

Flegr J, Stříž I. Potential immunomodulatory effects of latent toxoplasmosis in humans. BMC Infect Dis 2011; 11:274; PMID:22008411; http://dx.doi.org/ 10.1186/1471-2334-11-274 PubMed DOI PMC

Flegr J, Escudero DQ. Impaired health status and increased incidence of diseases in PubMed DOI

Gaskell EA, Smith JE, Pinney JW, Westhead DR, McConkey GA. A unique dual activity amino acid hydroxylase in PubMed DOI PMC

Prandovszky E, Gaskell E, Martin H, Dubey JP, Webster JP, McConkey GA. The neurotropic parasite PubMed DOI PMC

Torrey EF, Bartko JJ, Lun ZR, Yolken RH. Antibodies to PubMed DOI PMC

Torrey EF, Bartko JJ, Yolken RH. PubMed DOI PMC

Holub D, Flegr J, Dragomirecka E, Rodriguez M, Preiss M, Novak T, Čermák J, Horáček J, Kodym P, Libiger J, et al. Differences in onset of disease and severity of psychopathology between toxoplasmosis-related and toxoplasmosis-unrelated schizophrenia. Acta Psychiatr Scand 2013; 127:227-38; PMID:23126494; http://dx.doi.org/ 10.1111/acps.12031 PubMed DOI

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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 PubMed DOI

Skallová A, Novotná M, Kolbeková P, Gašová Z, Veselý V, Flegr J. Decreased level of novelty seeking in blood donors infected with PubMed

Skallová A, Kodym P, Frynta D, Flegr J. The role of dopamine in PubMed DOI

Hodková H, Kodym P, Flegr J. Poorer results of mice with latent toxoplasmosis in learning tests: impaired learning processes or the novelty discrimination mechanism? Parasitology 2007; 134:1329-37; PMID:17445326; http://dx.doi.org/ 10.1017/S0031182007002673 PubMed DOI

Silva NM, Rodrigues CV, Santoro MM, Reis LFL, Alvarez-Leite JI, Gazzinelli RT. Expression of indoleamine 2,3-dioxygenase, tryptophan degradation, and kynurenine formation during in vivo infection with PubMed PMC

MacKenzie CR, Heseler K, Muller A, Daubener W. Role of indoleamine 2,3-dioxygenase in antimicrobial defence and immuno-regulation: Tryptophan depletion versus production of toxic kynurenines. Curr Drug Metab 2007; 8:237-44; PMID:17430112; http://dx.doi.org/ 10.2174/138920007780362518 PubMed DOI

Beyond Latency: Chronic Toxoplasma Infection and Its Unveiled Behavioral and Clinical Manifestations-A 30-Year Research Perspective

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