We model the formation of a herd as a game between a predator and a prey population. The predator receives some information about the composition of the herd when he chases it, but receives no information when he chases a solitary individual. We describe situations in which the herd and its...

Gregarious behavior of potential prey was explained by Hamilton (1971) on the basis of risk-sharing: The probability of being picked up by a predator is small when one makes part of a large aggregate of prey. This argument holds only if the predator chooses its victims at random. It is not the...

In a number of papers on their theory of Inequity Aversion, E. Fehr and K. Schmidt have claimed that the theory explains the behavior in many experiments. By virtue of having an infinite number of parameters the theory can predict a wide range of outcomes, from the competitive to the...