Thanks for that very nice recap of intelligence testing. It must be frustrating to have to continuously defend your research area as something real.

I’d like to challenge you on the claim that controlling for social class (or other factors) allows for concluding that a true IQ-mortality connection exists. We could claim this only if we had perfectly accurate measures of socio-economic status, and our measures of SES are quite crude. If SES affects both IQ and mortality, and we measure SES imperfectly and then partial out that imperfect bit from IQ and mortality, then some of the remaining IQ-mortality correlation could still be due to the unmeasured remainder of SES.

Similarly, I’m not sure if it’s terribly well appreciated that being subjected to intelligence testing is a stressful experience. Since stress will lower test performance, then IQ scores might be picking up some measure of susceptibility to stress - which could be a predictor of achievement in its own right. Sometimes, it is claimed that IQ predicts something better than personality (for example the recovery from PTSD in war veterans). However, stress during personality assessment will not influence the results in any particular direction, and this might make IQ a better - if indirect - predictor of some kinds of stress-related failure.

Apart from that, I wonder if the denial of IQ relevance among well educated people simply has to do with restriction of range. Those who do intellectual work will have been selected for cognitive ability again and again at different stages of schooling, and will be surrounded with people who have been sifted through the same sieve. The differences in personality that lead to differences in achievement will stand out more starkly because of this.

Ana Todorović

Written by Ana Todorović