Height and intelligence

Epidemiological studies have shown that intelligence is positively correlated with height in human populations. Similar associations have been found in early and late childhood and adulthood in both developed and developing countries, and associations persisted after controlling for social class and parental education.

It should be noted that correlation does not imply causation. In this case, it seems unlikely either is caused directly by the other. Note also the correlation is far from absolute; These studies do not imply that there are no short people who are highly intelligent, or that changes in physical height have a direct effect on cognitive ability. Indeed, intelligence is believed to be influenced by many different factors, and individuals with a wide range of intelligence can be observed at any given height.

The reasons for the association between height and intelligence remain unclear, but possible explanations include that height may be a biomarker of nutritional status or general mental and physical health during development, that common genetic factors may influence both height and intelligence, or that both height and intelligence may be affected by adverse early environmental exposures. A large recent twin pair study of the height-intelligence relationship showed that both shared environment (59%) and shared genetics (35%) are responsible for significant portions of the observed correlation between intelligence and height.

Height has also been shown to have a positive correlation with adult income, raising the possibility that workplace discrimination based on height has a direct impact on income levels (see heightism). A recent study using four data sets from the US and UK found that after controlling for difference in cognitive test scores, there was no detectable independent effect of height itself on adult earnings, indicating that the height premium in adult earnings can be explained by childhood scores on intelligence tests However, others believe that height has a significant independent impact, pointing to specific instances of height-based discrimination. The relationship between height, cognitive ability, and discrimination based on height remains a subject of debate.