If a given speaker uses a syntactic form only once, does this single occurrence mean that this form is part of his or her linguistic competence? For example, I use a syntactic form like, "Who did you say where went?" on a single occasion. Is this syntactic form part of my linguistic competence? Or is it only an accident--not representative of my competence?

A linguistic database can help determine linguistic competence. Because linguistic databases include, from individual speakers, thousands of utterances, a researcher can study the database to determine if my single utterance represents my competence. But how can a researcher search through those thousands of utterances to locate just the one type of utterance?

A researcher uses special computer programs to search computerized linguistic databases for a given utterance. The combination of linguistic database and search programs saves the researcher a lot of time and energy. (However, it would not relieve the researcher of performing the linguistic analyses.)

In this course, we will learn the use of one type of linguistic database and its associated search programs. The linguistic database called CHILDES (Child Language Data Exchange System) includes many megabytes of naturalistic acquisitional data from children acquiring several different languages. The CHILDES search programs are called CLAN (Computerized Language Analysis) programs. MacWhinney's (1991) manual describes all the CLAN programs in detail. 

MacWhinney, B. (1991). The CHILDES Project: Tools for Analyzing Talk. Hillsdale, NJ: Lawrence Erlbaum Associates.