Display of behaviors that are helpful to others such that this motivates these same others to display helpful behaviors in return.

altruism results in what also can be described as , though with the mutually not necessarily occurring simultaneously but instead potentially alternating. Thus, a cooperative behavior today can be rewarded by a cooperative behavior in return sometime in the future.

Note that need not be of altruism but instead can consist of or behaviors instead, so-called . For keeping track of these various concepts, see for example the idea of a .