Is a Canadian-American cognitive psychologist, linguist, and popular science author. He is Johnstone Family Professor in the Department of Psychology at Harvard University, and is known for his advocacy of evolutionary psychology and the computational theory of mind. Pinker's academic specializations are visual cognition and psycholinguistics. His experimental subjects include mental imagery, shape recognition, visual attention, children's language development, regular and irregular phenomena in language, the neural bases of words and grammar, and the psychology of cooperation and communication, including euphemism, innuendo, emotional expression, and common knowledge. He has written two technical books that proposed a general theory of language acquisition and applied it to children's learning of verbs. In particular, his work with Alan Prince published in 1989 critiqued the connectionist model of how children acquire the past tense of English verbs, arguing instead that children use default rules such as adding "-ed" to make regular forms, sometimes in error, but are obliged to learn irregular forms one by one.