Mate choice for cognitive traits: a review of the evidence in nonhuman vertebrates

To what extent do individuals assess the cognitive abilities of the opposite sex when choosing a mate? With the exception of song learning in birds, the hypothesis that cognitive traits are under sexual selection has received attention only recently. Here, we evaluate the evidence for this hypothesis in nonhuman vertebrates. We first briefly review the literature on brain development, which shows that cognition may be a sensitive indicator of early developmental conditions. We then consider the empirical evidence that females choose mates with better cognitive skills, which may be reflected in males' courtship displays, foraging performance, courtship feeding, or diet-dependent morphological traits. There is very little research that assesses whether females discriminate between males through direct observation of cognitively demanding behavior. Instead, several studies support female choice on the basis of morphological traits correlated with cognitive abilities. We conclude by highlighting key questions for future research: 1) To what extent do cognitive skills determine foraging success, courtship feeding, and the expression of dietdependent morphological traits? 2) Do behavioral courtship displays depend on motor development and physiological maturation or learning through practice and experience? 3) How do cognitive abilities affect survival and mating success? Studies on a range of vertebrate taxa, with their diverse mating systems and cognitive ecologies, offer great potential to tackle these questions and deepen our understanding of sexual selection on cognition.