Psycholinguistics or linguistics of psychology is the study of the psychological and neurobiological factors that enable humans to acquire, use, and understand language. Initial forays into psycholinguistics were largely philosophical ventures, due mainly to a lack of cohesive data on how the human brain functioned. Modern research makes use of biology, neuroscience, cognitive science, and information theory to study how the brain processes language. There are a number of subdisciplines, with neurolinguistics and psycholinguistics being the two most popular.

Psycholinguistics covers the cognitive processes that make it possible to generate a grammatical and meaningful sentence out of vocabulary and grammatical structures, as well as the processes that make it possible to understand utterances, words, text, etc. Developmental psycholinguistics studies infants' and children's ability to learn language, usually with experimental or at least quantitative methods (as opposed to naturalistic observation like Darwin and Piaget emphasized when studying their own children).

Areas of study

Psycholinguistics is interdisciplinary in nature and is studied by people in a variety of fields, such as psychology, cognitive science, and linguistics. There are several subdivisions within psycholinguistics that are based on the components that make up human language.

1. Phonetics and phonology are concerned with the study of speech sounds. Within psycholinguistics, research focuses on how the brain processes and understands these sounds.
2. Syntax
3. Semantics
4. Pragmatics

Theories

One of the most famous psycholinguists is Noam Chomsky. Chomsky believed that humans have an innate Universal Grammar, an abstract concept containing the underpinnings for grammatical rules in all languages. This view emphasizes the point that children acquiring a language have a vast search space to explore among possible human grammars, yet somehow settle on the language(s) spoken or signed in the community of speakers. This view remains controversial.

Psychology pioneer Sigmund Freud wrote much on the influence between psychological and emotional states, particularly from the unconscious and language. Among his theories is that which developed into the notion of the Freudian slip. Much of his exploration of the topic can be found in his work.

Methodologies

Most research in psycholinguistics takes the form of psychophysical and behavioral experiments. In these types of studies, subjects are presented with some form of linguistic input and asked to give a particular response. Reaction times and proportion correct are the most often employed measures of performance.

More recently, eye tracking has been used to study online language processing. Beginning with Tanenhaus et al. (1995), a number of studies have begun to use eye movements as a tool for studying the cognitive processes related to language. Since eye movements are closely linked to the current focus of attention, language processing can be studied by monitoring eye movements as a subject is presented with linguistic input.

Other techniques include brain imaging and computational modeling. Each type of methodology presents a set of advantages and disadvantages for studying a particular problem in psycholinguistics.

Issues

There are a number of unanswered questions in psycholinguistics.

Developmental

How are infants able to learn language? Almost all healthy human infants acquire language readily in the first few years of life. This is true across cultures and societies. In addition, it is much more difficult for adults to acquire second languages than it is for infants to learn their first language (bilingual infants are able to learn both of their native languages easily). Thus, sensitive periods exists during which language is able to be learned readily. A great deal of research in psycholinguistics focuses on how this ability develops and diminishes over time. It also seems to be the case that the more languages one knows, the easier it is to learn more.

Machine learning/translation

Another unsolved problem in the field is how to create computer programs that can understand language as well as humans. This is closely related to computational linguistics and has many potential practical applications.