Performance of the independent and cooperative worker groups and the mongrels in Study 1. Columns show the group results of independent workers, cooperative workers and mongrels. Stars on top of the columns show significant difference compared to chance level (one sample t-test). Stars above the lines show significant difference between groups (ANOVA). * p < 0.05; ** p < 0.01; *** p < 0.001. The numbers in the columns show the percentage of the successful subjects within a group (measured at the individual level with binomial test).