Domain-specific theorists argue that these competencies are too sophisticated to have been learned via a domain-general process like associative learning, especially over such a short time and in the face of the infant’s perceptual, attentional, and motor deficits. Current proponents of domain specificity argue that evolution equipped humans with specific adaptations designed to overcome persistent problems in the environment. For humans, popular candidates include reasoning about objects, other intentional agents, language, and number. Researchers in this field seek evidence for domain specificity in a variety of ways. Some look for unique cognitive signatures thought to characterize a domain . Others try to show selective impairment or competence within but not across domains .Still others use learnability arguments to argue that a cognitive process or specific cognitive content could not be learned, as in Noam Chomsky’s poverty of the stimulus argument for language.