Ullman, M.T. and Pinker, S. Talk at the 15th Annual Boston University Conference on Language Development, Boston. Application of a regular rule is blocked if an irregular form for that word already exists. As children strengthened their lexical entry for broke , they would be impelled to stop saying breaked by this endogenous constraint. The same constraint prevents adults from applying the regular rule to verbs like break . The fact that doublets do occasionally arise, and are successfully retained across generations by a mechanism that seems to violate blocking, casts doubt on the existence of blocking as a strong mental constraint.
Lexical entries are memory representations and hence can be weak or inaccessible.
If an entry is weak, it will block the regular form only partially. We presented adult English speakers with regular and irregular past tense forms for 43 doublets. Each verb was presented in 4 sentences, twice as a regular, twice as an irregular, scattered in a randomized list. Subjects rated how natural each verb sounded on a 7-point scale. If survival of doublets is due to weak memory entries, they should occur more often for low-frequency verbs.