This chapter explores how evolutionary thinking can inform the generation and testing of hypotheses in cognitive science. From the unions of proximate and ultimate theories evolutionary psychologists have used several kinds of strategy for the generation of new theories and hypotheses. The most common of these is to use a combination of prior observation and a priori theoretical considerations to generate hypotheses about psychological adaptations. Psychological adaptations are frequently referred to as modules. Human psychological modules are likely to be modified versions of previously existing modules that inherit much of their problem-solving machinery, and evolve against a background of pre-existing modules with which they must be able to interface. Evolutionary psychology research has described a wide range of psychological mechanisms. These include mechanisms involved in mate choice, cooperation, decision making, face recognition, mindreading, language acquisition and production, kin detection and kin-directed altruism, and emotions.