Abstract
Psychologists believe grade schoolers' free play in the United States is universally biased toward single-gender groups. In a study of grade schoolers in a children's museum, already-acquainted kindergartners to sixth graders were observed at three exhibits. While boys chose more automobile play and girls more supermarketing, one-quarter of each group played in settings dominated by the other gender. Boys had no group-size preference; girls had a strong preference for small groups. That preference accounts for most of the gender differences found in children's gender sorting in a novel environment. However, the ubiquity of gender segregation in large groups of grade schoolers was disconfirmed for this setting.