Words and Rules: The Ingredients of Language is a 1999 popular linguistics book by Steven Pinker about regular and irregular verbs.
"Words and rules" is a theory that has been predominantly developed by Pinker. It has been popularly contextualized within the so-called "past-tense debate," which was sparked by Rumelhart and McClelland's 1986 connectionist model of the production of regular and irregular verbs. In essence, the Words and Rules theory states that past-tense forms of verbs arise from both declarative memory (as words) and procedural systems (from rules).
Main ideas
In his book, Pinker "tries to illuminate the nature of language and mind by choosing a single phenomenon and examining it from every angle imaginable." His analysis reflects his view that language and many other aspects of human nature are innate evolutionary-psychological adaptations. Most of the book examines studies conducted on the form and frequency of grammatical errors (such as overgeneralization in past-tense formation) in English (and to a lesser extent in German) as well as the speech of brain-damaged persons with selective aphasia. Pinker discusses neuropsychological dissociations in two types of aphasia: anomia and agrammatism. Anomic patients often produce fluent and generally grammatical speech despite having difficulty retrieving and recognizing words, which implies the lexicon is "more impaired than grammatical combination."
Research
The Words and Rules model contradicts previous orthodox Chomskyan ideas hypothesizing that several irregular past tense forms arise from rules applied to verbs with phonological similarities (as seen with the example of sleep, weep, and keep above). He particularly notes discrepancies that would arise in application of a rule-based theory, as in the verb steep and its past-tense form steeped as opposed to steep/stept. Pinker accepts the notion of pattern associators from the connectionist model, which states that families of irregular verbs obtain their past-tense forms from associations between the phonological features of these verbs and those of their irregular past-tense forms. Pinker found that some adults and children will form the past-tense form splung from the novel verb spling in line with the pattern seen in fling/flung and cling/clung. However, he shows research showing these sorts of generalizations to be exceedingly rare in comparison to the over-application of the regular past-tense rule to these verbs.