Many economists and biologists view cooperation as anomalous: animals (including humans) that pursue their own self-interest have superior survival odds to their altruistic or cooperative neighbors. However, in many situations there are substantial gains to the group that can achieve cooperation...

We study how the mechanisms of choice influence preferences when animals face more than 2 alternatives simultaneously. Choice mechanisms can be hierarchical (if alternatives are assigned to categories by their similarity and choice is between categories) or simultaneous (if options enter the...

Social foraging differs from individual foraging because it alters both resource availability and the forager's behavior. We examined responses of starlings to the presence of conspecifics by manipulating foraging-group density experimentally, while ensuring that each subject's foraging...

We investigated the influence of energetic state at the time of acquaintance with a new food source on preference for that source on later encounters, using wild-caught European starlings as subjects. Twelve birds learned to obtain food rewards by pecking at either of two keys identified by...