Comparative evaluation and its implications for mate choice.

Experiments on decision making by humans show that the choices that we make can be very labile. The magnitude of our preferences, and even our rank ordering of options, can vary according to the number and type of alternatives available for comparison. This apparent irrationality has been argued to result from our use of decision heuristics that have evolved to enable us to choose quickly and efficiently between options differing in multiple attributes. Here, we argue that, because there is also selective pressure for animals to make mating decisions quickly, and because potential mates also differ in multiple attributes, similar decision heuristics might have evolved for mate choice. Following this reasoning, the attractiveness of a given mate will depend on the others with whom he or she is being compared, rather than being an absolute function of his or her underlying quality. We describe some of the ramifications of such comparative evaluation, and argue that it could offer new insights into some of the biggest outstanding problems in mate choice and sexual selection.