This study examined the effects of children's cognitively based role expectations on their judgments of the grammatical acceptability of sentences. Sixty children, 12 each in grades 4 through 8, individually heard 10 sentences violating the Minimum Distance Principle (MDP). The sentences were grammatical, but linguistically complex, and violated the children's expectations. Children were asked a comprehension question, asked whether the sentence was acceptable, and asked to identify any aspect of the sentences that was unacceptable. Children's responses yielded 4 categories of unacceptable elements: structure, agent, verb tense, and promise. Grade level was not a significant source of variance. Expectations affected judgments, thus lending support to interest among psycholinguists in extra-linguistic variables in sentence processing. Care should be taken to design materials controlling for the non-syntactic aspects of children's expectations so that such factors do not confound the measurement of syntactic acquisition. (AM)