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The study of height and intelligence is the analysis of how variations in height affect human intelligence. Some epidemiological research on the subject has shown that there is a small but statistically significant positive correlation between height and intelligence after controlling for socioeconomic class and parental education. This correlation arises in both the developed and developing world and persists across age groups. There is no scientific consensus on why this correlation arises but one possible explanation is that height may act as a biomarker for nutritional status and health during intellectual development. One such theory argues that since height strongly correlates with white and gray matter volume, it may act as a biomarker for cerebral development which itself mediates intelligence. Competing explanations include that certain genetic factors may influence both height and intelligence, or that both height and intelligence may be affected in similar ways by adverse environmental exposures during development. Other explanations further qualify the positive correlation between height and intelligence, suggesting that because the correlation becomes weaker with higher socioeconomic class and education level, environmental factors could partially supercede any genetic factors affecting both characteristics.

Correlation
Studies of developing adolescents and young adults indicate a very small positive correlation between human IQ and height within national populations. The association is supported by studies linking height at eighteen with subsequent scholarly performance.

Correlation coefficients in developing children are typically about 0.2. A large study conducted on Norwegian soldiers the correlation between height and general ability was. The effect appears to hold into the extremes of stature, but may decrease with age.

The correlation between the two factors is weak, although statistically significant. Consequently, these studies do not imply that variations in stature have a direct effect on cognitive ability. However, similar strength correlations have been found in early and late childhood in both developed and developing countries, even after controlling for social class and parental education. In adults, changes in environment and social status reduce the strength of this correlation.

A study in 2006 by Anne Case and Christina Paxson attracted media attention.

Explanations of the correlation
The reasons for the association between height and intelligence remain unclear, but possible explanations include that height may be a marker of nutritional status, prenatal maternal stress, or general mental and physical health during development.

It has been suggested that the large increases in average height, assumed to be due to improved nutrition, have been accompanied by an increase in brain size which may be one explanation for the Flynn effect.

Studies have shown, however, that common genetic factors influence variation in both height and intelligence, and are responsible for some of the effect, or that both height and intelligence may be affected by adverse early environmental exposures. Two large recent twin pair studies of the height-intelligence relationship showed that both shared environment (59% in both studies) and shared genetics (35% in one study and 31% in the other) are responsible for significant portions of the observed correlation between intelligence and height.