Changes with Age in the Strategy of Social Behavior

Abstract

The theory of kin selection states that altruistic behaviour will be favored so long as the cost to the donor is less than the benefit to the recipients suitably discounted by their degree of relatedness. These “costs” and “benefits” are to be measured in terms of marginal changes in the reproductive values of the individuals concerned and will depend critically on a number of factors, such as sex, size, stage in life history, etc. We introduce two intervening variables, “eligibility” and “generosity,” to facilitate an analysis of how costs and benefits of social interactions would relate to such factors. An individual’s eligibility to receive social help will peak in early childhood, while its generosity to donate social help will peak in late adulthood. Both eligibility and generosity will be low at adolescence which would be a period of most intense competitive interactions. Cooperative behavior would be most favored during life history stages with high levels of generosity.