Grammatical intuitions about irregular verb inflections

If people possess a rule that the root of a verb plus -ed produces the past tense, why does this rule produce an unacceptable form when applied to an irregular verb (e.g., comed)? One possibility is that the unacceptability of comed is the result of lexical priming. That is, comed primes the correct form came, and the awareness of came causes comed to be perceived as unacceptable. If so, then the acceptability of a misinflected form should be determined by the factors that influence the priming of its correct form, such as the frequency and hence speed of retrieval of its correct form. Three experiments were conducted. In Experiment 1, subjects were faster to reject misinflected irregular verbs when the correct irregular form had a higher frequency than when it had a lower frequency. Furthermore, the higher the frequency of the correct form, the more unacceptable the misinflected form seemed. Experiment 2 used the naming task to confirm that the presentation of a misinflected form facilitated the naming of its correct form. In Experiment 3, subjects were faster to accept an irregular verb when it was primed by a misinflected irregular verb than with a correct regular verb. This was taken as evidence that the misinflected irregular verb accesses the correct form.