Eleanor Maccoby and Carol Nagy Jacklin conducted a study in 1974 that suggested no noticeable difference in overall cognitive ability. Girls exhibited very minor superiority in verbal skills, and boys exhibited very minor superiority in visual-spatial skills. Mathematics, however, were more complex.
Girls learn basic language before boys do. They speak their first words about half a month (on average) before boys do. They learn more vocabulary quicker, and they generally pronounce words better than boys. High School girls seem to be superior to boys in spelling, reading comprehension, vocabulary, punctuation and in solving analogies. Many more boys than girls have reading problems throughout all ages of development, ranging from simple problems to severe disabilities. However, boys seem to catch up to girls in language skills at about the age that they go to college.
Mathematics are, as said above, more complex. Contrary to popular belief, males are not better than females at math. Females actually show superiority during elementary school in computational ability. Males do, however, excel in mathematical problem solving ability. The perceived mathematical inferiority of females is often based on the Scholastic Aptitude Test (SAT), which is administered to high school juniors and seniors. The SAT's math section is mostly mathematical problem solving, which accounts for the difference in scores by gender (twice as many boys than girls receive scores of 500 or more).
So, the perceived differences in intelligence between girls and boys are true, but not on the same scale as most people believe. The actual differences are very small, and may largely reflect sociocultural expectations and environmental influences rather than actual biological differences. These differences are getting smaller, and we must remember that there are always exceptions to this "rule." There will always be great women physicists and great men playwrights.
Males apparently excel in visual-spatial abilities. Beginning in adolescence, boys usually outperform girls on tests of spatial ability which assess skills such as mentally rotating figures in space and finding figures embedded within larger designs.