On rules and exceptions: An investigation of inflectional morphology

This thesis examines two theories of the acquisition and representation of inflection (e.g. English past tense formation), focusing on children's overregularization errors such as goed and wented. On the "rule" view, suggested by Pinker and Prince (1988), regular forms are created by the on-line application of symbolic, default rule (add -ed to form the past tense), while irregular forms are retrieved from an associative memory. The alternative "connectionist" view, suggested by Rumelhart and McClelland, is that systems of rule and exceptions could be represented by single uniform associative connectionist network which contains no rules.

Parts 2 and 3 focus on children's overregularization errors, such as foots and mans. On the symbolic view, such errors are caused by the application of the default rule whenever an irregular cannot be retrieved from memory. On the connectionist view, overregulations are caused when irregular words are drawn by an analogical process to regular words. A study of 11,521 irregular past tense utterances in the spontaneous speech of 83 children. The major results were as follows: (1) Overregularization errors are relatively rare. (2) Overregularization occurs at a roughly constant low rate from the two's into the school-age years, affecting most irregular verbs. (3) Though overregularization errors never predominate, one aspect of their purported U-shaped development was confirmed quantitatively: an extended period of correct performance precedes the first error. (4) Overregularization does not correlate with increases in the number or proportion of regular verbs in parental speech, children's speech, or children's vocabularies. (5) Overregularizations first appear when children begin to mark regular verbs for tense reliably. (6) The more often a parent uses an irregular form, the less often the child overregularizes it. (7) Verbs are protected from overregularization by similar-sounding irregulars, but are not attracted to overregularization by similar-sounding regulars.

Contrary to connectionist accounts, these effects are not due to regular words being in the majority. The German participle -t and plural -s apply to minorities of words. Two experiments eliciting ratings of novel German words show that the affixes behave like their English counterparts, as defaults. Thus default suffixation is not due to numerous regular words reinforcing a pattern in associative memory, but to a memory-independent, symbol-concatenating mental operation. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)