Limited interaction in speech production: Chronometric, speech error, and neuropsychological evidence

Results from chronometric and speech errors studies provide convergent evidence for both lower and upper bounds on interaction within the speech production system. Some degree of cascading activation is required to account for patterns of speech errors in neurologically intact and impaired speakers as well as the results of recent chronometric studies. However, the strength of this form of interaction must be limited to account for the occurrence of selective deficits in the production system and restrictions on the conditions under which interactive effects influence reaction times. Similarly, some amount of feedback from phonological to word-level representations is necessary to account for patterns of speech errors in neurologically intact and impaired individuals as well as the influence of phonological neighbours on response latency. This interactive mechanism must also be limited to account for restrictions on the types of speech errors produced following selective deficits within the production system. Results from a variety of empirical traditions therefore converge on the same conclusion: interaction is present, but it must be crucially limited.