Intelligence and educational level in adult males at the extremes of stature.

Stature and intellectual ability are commonly found to correlate positively (r approximately 0.2). In this study we have assessed whether this relationship holds true at the extremes of stature in adults. From a representative study population of 76,111 young Danish men, we defined an extremely short group as those below the 2d percentile (less than or equal to 163 cm) and an extremely tall group as those above the 98th percentile (greater than or equal to 191 cm). The short group had intelligence test scores and educational levels lying at approximately two-thirds of a standard deviation below the overall means. The tall group had means lying approximately one-half standard deviation above the overall means. These deviations are to a large degree in agreement with the observed overall correlations of height with intelligence test scores (r = 0.244) and with educational level (r = 0.264). Both groups, however, appear to score somewhat below the levels expected from a purely linear relationship. For the short group there appear to be local factors that are particularly detrimental to intellectual ability. For the tall group corresponding local factors are relatively independent of intellectual ability.