Testosterone levels as modifiers of psychometric g

In large samples of American armed forces veterans, those below the first percentile and above the 99th percentile in serum testosterone level show significantly and considerably lower g factor scores derived from a battery of 19 diverse psychometric variables. Between these extremes of testosterone level, however, there is little relationship between testosterone and psychometric g. Factors orthogonal to g were also affected only at the extremes of testosterone level.