High IQ differences between rh- and rh+ with and w/out Toxoplasmosis

I have often heard the claim that rh negatives tend to have a higher IQ on the average than rh positives. It is one of many claims people just seem to run with. And when I ask for proof, they have none.

Never believe anything unless you can verify it for yourself. And if you don’t have time to do your own research, don’t promote claims as fact.

I am not referring to “intuition” or “EQ”. But actual IQ score. And what we need is actual data. Not claims or feelings. So in an effort to get closer to reality, here is actual data available which may or may not bring us a step or two further:

Toxoplasmosis-Associated Difference in Intelligence and Personality in Men Depends on Their Rhesus Blood Group but Not ABO Blood Group examines differences in IQ scores separated between rh negative and rh positive subjects as well as those who have Toxoplasmosis and those who don’t. How being infected with the Toxoplasma gondii virus affects rh negatives and rh positives differently has been the ongoing theme of many studies Prof. Jaroslav Flegr has initiated. And this one actually does show differences in IQ scores. But it may not be what you’ve expected.

What strikes me intitially is that in this study, the IQ scores of rh negatives not infected with the virus scored a lot lower than rh positives not infected with the virus.

A median IQ score for rh negatives of 96 for nonverbal and 97 for verbal is unexpectedly low.

Rh positives not infected show 102 median for both, nonverbal and verbal.

A 6 and 5 point difference is significant.

But here is where it becomes interesting:

When measuring the results of those who are infected with Toxoplasma gondii, the results for rh positives stay the same for nonverbal at 102 and go down one point to 101 for verbal tests.

How about in rh negative subjects?

A 10 point jump to 106 for nonverbal and a 9 point jump to 105 for verbal tests.

This is a study involving 502 male subjects from the Czech military, so take that into account. If you wish to conclude average IQ scores based on these results, keep in mind that in Europe based on location, around 20%-60% of the population is infected with Toxoplasma gondii.

Most of the effects of the virus tend to be increased negative ones on rh negatives while for still to be explained reasons rh positives can even see performance increases due to Toxoplasmosis. But not when it comes to IQ scores.

How can this be?

It has long been proven, that IQ scores are also dependent on environmental factors and not just genetics. What we are dealing with is two types of factors:

1) A person’s potential

We don’t use all of our capacities and there are influences which activate our brain power and those hindering them from performing properly. Genetic predispositions suggest that even with environmental factors playing a role, the range of expected outcomes is one not as likely to change. The only problem is that this one is tough to measure and studies like the one highlighted in this post can help attribute to such.

2) Environmental impacts

This study screams for answers in terms of causation. One of many other studies concludes:

In the present study, we found that various environmental factors such as place of residence, physical exercise, family income, parents’ occupation and education influence the IQ of a child to a great extent. Hence, a child must be provided with an optimal environment to be able to develop to his/her full genetic potential.

It is also possible, that stress can impact you very negatively, yet also bring out abilities in you which are dormant, but rarely used when not required. A lot more needs to be done research wise, but this is a start.