Discreteness and interactivity in spoken word production.

Five theories of spoken word production that differ along the discreteness-interactivity dimension are evaluated. Specifically examined is the role that cascading activation, feedback, seriality, and interaction domains play in accounting for a set of fundamental observations derived from patterns of speech errors produced by normal and brain-damaged individuals. After reviewing the evidence from normal speech errors, case studies of 3 brain-damaged individuals with acquired naming deficits are presented. The patterns these individuals exhibit provide important constraints on theories of spoken naming. With the help of computer simulations of the 5 theories, the authors evaluate the extent to which the error patterns predicted by each theory conform with the empirical facts. The results support a theory of spoken word production that, although interactive, places important restrictions on the extent and locus of interactivity.