The persistence of optional complementizer production: Why saying "that" is not saying "that" at all

What kinds of processing mechanisms determine the forms of spoken sentences? Three experiments (N=176) measured whether the mention of an optional that in a sentence-complement structure (“The mechanic mentioned (that) the car could use a tune-up”) can be primed by the prior production of a sentence that included a lexically or a lexically and syntactically similar that, using a recall-based sentence-production task. Results showed that target that-mention was influenced by primes with lexically and syntactically similar thats (sentence-complement primes with versus without thats), but not by primes with only lexically similar thats (transitive primes with determiner thats, "The company insured that farm for...," or noun-complement primes with complementizer thats, "The theory that..."). Also, compared to neutral primes, sentence-complement primes without thats decreased target that-mention more than sentencecomplement primes with thats increased it. This suggests that complementizer-persistence specifically and sentence-production generally includes an autonomous, lexically independent syntactic processing component.