The science and politics of studying sex and gender. Prior to 1973, little attention was paid to sex differences. Research used only participants of one sex, most often males. Elanor maccoby and carol jacklyn changed this by publishing the psychology of sex. Concluded that women were slightly better than men at verbal ability. Men were slightly better than women in math ability and spatial ability. Since maccoby and jacklyn"s research, researchers have developed a more precise quantitative procedure for examining conclusions across studies. Meta analysis allows researchers to calculate with greater objectivity and precision whether a particular difference such as sex, is consistent across studies. Furthermore, it also researchers to estimate how large the difference actually is this is the effect size. D statistic: used to express a difference in standard deviant units. A d of . 50 means that the average difference between two groups is half a standard deviant.