sexual masochism

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 m anipulates 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, or smell of leopards in chimpanzee, start to additionally co - activate se xual arousal - related circuits in the infected rodents. 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 masochi sm 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 n ee d 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