Most buyers will also be in an emotional state. If you can remember that you are selling not just a piece of property but also an image, a dream and a lifestyle, you'll be more likely to put in the extra effort of staging and perhaps some minor remodeling to get top dollar for your home.
The branch of linguistics concerned with linguistic performance, that is, the production and comprehension of speech (or of sign language by the deaf), is called psycholinguistics. Psycholinguists also investigate how children acquire the complex grammar that underlies language use.
Language acquisition is one of the central topics in cognitive science. Every theory of cognition has tried to explain it; probably no other topic has aroused such controversy. Possessing a language is the quintessentially human trait: all normal humans speak, no nonhuman animal does.