activities can crowd out motivation to perform these activities. More recent work highlights nuanced and important features … motivation may not be a concern in many contexts, the substitution of one prosocial activity for another or shifts in activities …

other. We show that altruism has a non-monotonic effect on effort. We study how this effect depends on "climate," the … robustness depends on climate. We find that family ties will be stronger in milder climates than in harsher climates. -- altruism …

produce output under uncertainty, and siblings may transfer output to each other. We show that altruism has a non …-monotonic effect on effort. Equilibrium effort decreases (increases) with altruism at low (high) levels of altruism. We study how this … climates than in harsher climates, and that the evolutionarily robust degree of altruism is positive but less than one half …