Fig. 4: Participants over-exert to earn rewards for themselves and in poorer foraging environments.

Overall, participants in study 3 (n = 54) exerted significantly more physical force when trying to win potential rewards for themselves than for others (b = −0.054 [−0.074, −0.034], z = 5.52, p < 0.001). There was a significant interaction between environment and expected value, which showed that participants tended to exert more force in the poor environments when the expected value was higher (b = −0.016, [−0.026, −0.005], z = 2.94, p = 0.003). AUC area under the curve; shaded bands around the lines represent 95% confidence intervals of the mean; ^**p < 0.01, ^***p < 0.001; all tests were two-sided Wald Z-tests.