From this paper
Consistent and significant differences in Cattell’s personality factors were found between Toxoplasmainfected and -uninfected subjects in 9 of 11 studies, and these differences were not the same for men and women.
and
Those with latent infection performed significantly more poorly (analysis of covariance, P = 0.011) and appeared to lose their concentration more quickly, although the effect of the infection was modest and explained less than 10% of the variability in performance. Similar results were recently obtained in 2 (unpublished) studies performed on 439 blood donors and 623 military servicemen.
Explaining ~10% of the variance actually seems fairly high to me.
Explaining ~10% of the variance actually seems fairly high to me
How high is the sky? That is, 10% of the variance might be a lot, but what is the variance like? In other words, what magnitude of effect should you expect from getting cured of toxo? How many IQ points would that get you? (Or whatever scale matters to you...)
Toxoplasmodi gondii is a parasitic protozoa who's primary host is cats but also infects other mammals, primarily mice and rats but including humans, as part of its life cycle. Infection by Toxoplasmodi gondii is called Toxoplasmosis and may be acute (flu like symptoms) or latent.
Toxoplasmosis is extremely common. Worldwide, about 30% (US 11%; France 88%!) of people about of people have Toxoplasmosis.
Toxoplasmosis is known to cause behavioral changes in rats:
Observational studies suggest that latent Toxoplasmosis may also cause behavioral changes in humans (source paper). The observed differences between infected people and non-infected people include: