Sex Differences in Abstract Ability of Volunteers and Nonvolunteers for Concept Learning Experiments

The primary aim of this study was to assess sex differences in intelligence, particularly abstract thinking ability, of 280 volunteers and nonvolunteers for concept learning experiments. A volunteer was defined as one who actually participated in the experiment. The results showed that male volunteers had significantly higher abstract thinking scores than male nonvolunteers but all other comparisons were nonsignificant. The present results underscore the necessity for controlling for differences in abstract thinking and sex in volunteers for conceptual studies.