A team from the Institute of Psychiatry analysed data from former US soldiers who served during the Vietnam war era.
They found that those who performed better on intelligence tests tended to have more – and more mobile – sperm.
They found a small, but statistically significant link, and were able to show that this could not be explained by unhealthy habits, such as smoking or drinking alcohol.
The study was based on 425 men who undertook several intelligence tests and provided semen samples.
The researchers found that independently of age and lifestyle, intelligence was correlated with all three measures of sperm quality – numbers, concentration, and ability to move.
I can barely begin to list the implicit assumptions these researchers are making, starting with the notion that army-administered intelligence tests a) measure intelligence b) aren’t simply correlated with socioeconomic status, which has a strong general health effect in the US c) aren’t correlated with non-lifestyle health issues that would affect sperm quality. And that’s before you even get into the subset of soldiers who would volunteer or be selected for the study. It’s possible that in a sample of 425 they managed to deal with all this, but I’m going with Runyon’s Law.