<P> The social norm of reciprocity is the expectation that people will respond to each other in similar ways--responding to gifts and kindnesses from others with similar benevolence of their own, and responding to harmful, hurtful acts from others with either indifference or some form of retaliation . Such norms can be crude and mechanical, such as a literal reading of the eye - for - an - eye rule lex talionis, or they can be complex and sophisticated, such as a subtle understanding of how anonymous donations to an international organization can be a form of reciprocity for the receipt of very personal benefits, such as the love of a parent . </P> <P> The norm of reciprocity varies widely in its details from situation to situation, and from society to society . Anthropologists and sociologists have often claimed, however, that having some version of the norm appears to be a social inevitability . Reciprocity figures prominently in social exchange theory, evolutionary psychology, social psychology, cultural anthropology and rational choice theory . </P> <P> One - to - one reciprocity. Some reciprocal relationships are direct one - to - one arrangements between individuals, or between institutions, or between governments . Some of these are one - time arrangements, and others are embedded in long - term relationships . Families often have expectations that children will reciprocate for the care they receive as infants by caring for their elderly parents; businesses may have long - term contractual obligations with each other: governments make treaties with each other . </P>

The concepts of loyalty and reciprocity are related