The Development of Extraversion, of Ability, and of the Relation Between Them

S ummary . Extraversion, as tested by Eysenck and his followers, is found on average to increase from 7 years to 13 years, and to decrease from youth to middle age; there appears to be a peak normally at 13 or 14 years. On the other hand, general ability increases until the twenties. If we assume that a person who is ahead (or behind) in one of these developments is also likely to be similarly ahead (or behind) in the other development, then this explains a general finding asserted by Eysenck and Cookson (1969) and others in this Journal , namely that the correlation between extraversion and ability is positive in young children and negative in older pupils and students. Some other, related, findings are also explained in the same way.