Il s’agit là du principal point de désaccord entre Richard Lynn et Arthur R. Jensen, ce dernier considérant que les hommes et les femmes ne montrent pas de différence significative de QI moyen. Richard Lynn considère qu’il y a bien différence, et explique celle-ci par les rythmes de développement différents : les filles atteindraient plus rapidement leur QI adulte, mais serait ensuite rattrapée et dépassée par les garçons, ce que confirme cette nouvelle étude.
A noter que l’écart trouvé par Colom & Lynn à l’âge de 18 ans est de 4,3 points, ce qui est extrêmement proche de celui calculable à partir de la différence de volume des cerveaux (4,4 points).
The consensus view states that there are no sex differences in intelligence. However, Lynn (1994, 1999) has formulated a developmental theory of sex differences in intelligence that challenges that view. The theory states that boys and girls mature at different rates such that the growth of girls accelerates at the age of about 9 years and remains in advance of boys until 14-15 years. At 15-16 years the growth of girls decelerates relative to boys. As boys continue to grow from this age their height and their mean IQs increase relative to those of girls. This paper presents new evidence for the theory from the Spanish standardization sample of the fifth edition of the DAT. 1027 boys and 924 girls between 12 and 18 years were tested. The general trend shows that girls do better at the younger ages and their performance declines relative to boys among older age groups, which supports the developmental theory. The sex difference for the DAT as a whole for 18 year olds is a 4.3 IQ advantage for boys, very close to the advantage that can be predicted from their larger brain size (4.4 IQ points). The profile of sex differences in abilities among the Spanish sample is closely similar to that in the United States and Britain, which is testimony to the robustness of the difference in these different cultures.
 Colom & Lynn (2003) : Testing the developmental theory of sex differences in intelligence on 12-18 year olds Personality and Individual Differences, Volume 36, Issue 1 , January 2004, Pages 75-82