It may seem merely a cliche born of centuries of educated people straining their eyes in dimly-lit libraries, but new genetic research suggests those who wear glasses really are more intelligent.
Researchers at the University of Edinburgh analyzed the genetic data of more than 44,480 people.
They found that, overall, those who were more intelligent were nearly 30 per cent more likely to have genes indicating they require reading glasses than those who scored poorly.
Published in the journal Nature Communications, the research also linked higher cognitive ability to genes known to play a part in better cardiovascular health.
The results are based on the most thorough investigation of intelligence genes of its kind to date.
The research team examined 148 genomic regions related to better cognitive function, including 58 that have not previously been reported.
They said the results could help understanding of the declines in cognitive function that happen with illness and as people age.
Because of the study’s design it not possible to say why there is a genetic correlation between intelligence, poor eyesight and cardiovascular health.
However, Dr Gail Davies, of University of Edinburgh’s Centre for Cognitive Ageing and Cognitive Epidemiology, who led the analysis, said: “This study, the largest genetic study of cognitive function, has identified many genetic differences that contribute to the heritability of thinking skills.
“The discovery of shared genetic effects on health outcomes and brain structure provides a foundation for exploring the mechanisms by which these differences influence thinking skills throughout a lifetime.”
Those who participated in the study had all taken a variety of thinking tests which were summarised as a general cognitive ability score.
All had genetic testing that examined their DNA and none of the people had dementia or a stroke.