This article's factual accuracy is disputed. Please help to ensure that disputed statements are reliably sourced. See the relevant discussion on the talk page.(December 2012)

l; Several epidemiological studies have shown a weak but statistically significant positive correlation between height and intelligence in human populations.[1][2][3][4] 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. This does not imply that many short people are not intelligent, or that changes in physical height have a direct effect on cognitive ability. The reasons for this association remain unclear, but possible explanations include that height may be a biomarker of nutritional status or general mental and physical health during development, that genetic factors may influence both height and intelligence, or that both height and intelligence may be affected by adverse early environmental exposures.

Contents

Studies of developing adolescents [5][6][7][8][9] and young adults[10][11] 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.[12]

Correlation coefficients in developing children are typically about 0.2. [13][14] A large study conducted on Norwegian soldiers the correlation between height and general ability was .15.[15] The effect appears to hold into the extremes of stature,[16] but may decrease with age.[17]

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.[17]

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.[21]

Studies have shown, however, that common genetic factors influence variation in both height and intelligence, and are responsible for some of the effect,[22] 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.[11][15]

^Walker SP, Grantham-McGregor SM, Powell CA, Chang SM. Effects of growth restriction in early childhood on growth, IQ, and cognition at age 11 to 12 years and the benefits of nutritional supplementation and psychosocial stimulation. J Pediatr 2000; 137:36–41.

^Walker SP, Grantham-McGregor SM, Powell CA, Chang SM. Effects of growth restriction in early childhood on growth, IQ, and cognition at age 11 to 12 years and the benefits of nutritional supplementation and psychosocial stimulation. J Pediatr 2000; 137:36–41. Abstract