Toward wild psychometrics: Linking individual cognitive differences to fitness

Abstract

Our understanding of the processes underlying animal cognition has improved dramatically in recent years, but we still know little about how cognitive traits evolve. Following Darwinian logic, to understand how selection acts on such traits we must determine whether they vary between individuals, influence fitness, and are heritable. A handful of recent studies have begun to explore the relationship between variation in individual cognitive performance and fitness under natural conditions. Such work holds great promise, but its success is contingent on accurate characterization and quantification of the cognitive differences between individuals. Existing research has typically adopted a "problem-solving" approach, assuming that individuals that complete novel tasks have greater cognitive prowess than those that do not. We argue that this approach is incapable of determining that individual differences are due to cognitive factors. We propose the adoption of psychologically grounded psychometric testing and discuss the criteria necessary to examine the fitness consequences of cognitive variation in the wild.