Speech production is the process by which a speaker converts an intended meaning into a grammatical set of words from which a listener can reconstruct that meaning. The study of speech production is important in the fields of psycholinguistics and syntax because it provides us with information about how the human brain constructs sentences. The majority of the evidence that linguists have concerning the process of speech production comes from the study of speech errors. Cairns gives seven steps in the process of speech production: idea, sentence meaning, lexical retrieval and creation of structure, application of phonological and morphological rules, phonological representation, instructions to the articulators, and production of speech. (1) However, there is some controversy over whether syntactic structure is represented prior to choice of lexical items, or vice versa. (2)

Those who prefer the syntax-first model cite speech errors in which an incorrect word is selected while the syntactic structure remains intact, that is, that selection errors almost always occur between words of the same grammatical class or part of speech. This suggests that the syntax of an utterance has already been chosen by the time that words are “slotted in” to their places according to their grammatical classes. (2)

Proponents of a words-first model of speech production note that it would be impossible for one to construct a grammatical sentence without some idea of which words will be employed. For example, the syntax of “John claimed to be able to eat a live frog” must depend on the word "claim," since other words of similar meaning would occur in different constructions; that is, we cannot substitute the word “asserted” or “declared” for “claimed” and have the sentence remain syntactically sound. (2) "Claim" must affect the syntax of the sentence and therefore must be chosen prior to syntactic construction.

Aitchison suggests that we may start to construct a phrase with one key word in mind (“claim”, for example) then build a syntax around it, and later slot in the rest of the words to convey the intended meaning. That would indicate that words are stored with their corresponding syntactic structures (e.g. eat (verb): NP –eat– NP), and that when constructing a sentence, we build the syntactic trees from the bottom upwards, filling in the appropriate phrases to convey the meaning grammatically. (2)

Speech production can be affected by several speech disorders, including aphasia and dysphasia.

Sources:
(1) Cairns, Helen Smith. Psycholinguistics. PRO-ED Inc. Austin, Texas. 1999. Print.
(2) Aitchison, Jean. The Articulate Mammal. Hutchinson & Co. London, UK. 1976. Print.