The role of instructions in the variability of sex-related differences in multiple-choice tests

When both experts and lay people interpret data on sex-related differences, they usually forget that the instruments for data collection might be provoking such differences. This experiment, carried out on 240 participants, focused on the effects of four instruction/scoring conditions on sex effect size in two computerized tests — vocabulary and mental rotation, for which sex-related differences had been shown to be, respectively, small (favoring females) and large (favoring males). Given the caution which seems to characterize female performance, our general hypothesis predicted that, under instructions encouraging guessing, effect sizes favoring males would augment and effect sizes favoring females would diminish. The opposite results were expected under instructions discouraging guessing. Some supporting evidence was found.