Psycholinguistics is the study of how humans acquire, interpret, and use language. The study includes both the psychological factors and the neurobiological factors involved. As a field, it has grown out of interdisciplinary work in fields such as cognitive psychology, neuroscience, applied linguistics, and information theory.
Linguist and social critic Noam Chomsky was a pioneer in psycholinguistics, arguing that all normal humans have an innate language ability and that all human languages have a common underlying structure known as universal grammar. This directly challenges behavioral learning theories, which argue that language is not innate but learned step by step through imitation and reinforcement. This is an ongoing debate.
Language acquisition is an important subtopic in psycholinguistics, and has been most commonly studied in young children who are learning their native language. Second language acquisition is also a topic of study in this field, investigating questions such as why learning a second language is easier for children than for most adults. It also questions why non-native speakers can have trouble distinguishing between and pronouncing certain sounds necessary for meaningful speech in their second language when these sounds are not present or distinct in their native language.
Speech perception is another focus in psycholinguistics and deals with how humans comprehend and process speech in real time. The TRACE model is a theory of speech perception in which interactions between different processing units allow people to process speech as they hear it. Computer simulations of the TRACE model have been built and are used to test how people process speech, particularly at the phoneme level — the smallest meaningful unit of sound.
Neurolinguistics is a field that is closely related to psycholinguistics, specifically focused on the brain's physiological reactions associated with language. Scientists in this field use brain imaging and other neuroscience-based techniques to investigate theories that mainly come from psycholinguistics and theoretical linguistics. Research on aphasias is also important in neurolinguistics. Aphasias are linguistic deficits, such as losing the ability to form coherent and meaningful sentences, as in Wernicke aphasia, that occur as a result of brain damage.
Psycholinguistic research has also been applied in other fields. These include the study of reading and writing in educational psychology, how animals associate sound with meaning in the study of animal language, and the development of artificial intelligence systems in computer science. It continues to develop as a complex, interdisciplinary field of study.