1) Linguist 2) Linguistic scientist 3) Psychologist 
A psycholinguist is a social scientist who studies Psycholinguistics. 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. More sp...
[n] - a person (usually a psychologist but sometimes a linguist) who studies the psychological basis of human language
noun a person (usually a psychologist but sometimes a linguist) who studies the psychological basis of human language