Fig. 5

Males show higher boxing frequency. a Males displayed a higher frequency of boxing behavior in both same- and mixed-sex pairs (Student’s t tests with Welch’s correction: **p < 0.01). There were no significant changes in frequency of boxing behavior dependent on the sex of the play partner (paired t tests: ns = not significant). b Separation of boxing behavior into individual days did not reveal a significant interaction between age and pair type (two-way repeated measures ANOVA). c Comparison of play on PN32 (familiar partner) and PN33 (novel partner) did not reveal an interaction between pair type and partner familiarity (two-way repeated measures ANOVA: ns = not significant)