Semantic and phonological factors in speech production: Evidence from picture-word interference experiments

Discrete models of speaking maintain that semantic-syntactic and phonological representations are largely independent, whereas interactive accounts allow for mutual influence between them. The studies presented here investigated this issue by employing a task in which participants named pictures while instructed to ignore visually or auditorily presented distractor words. Previous results using this paradigm with auditory distractors have been used to support the discrete view (e.g., Schriefers, Meyer, & Levelt, 1991) whereas results with visual distractors have been used to argue for an interactive account (e.g., Starreveld & La Heilj, 1996a). The first two experiments served to clarify the discrepancy across distractor modalities. Experiment 1 demonstrated that with auditorily presented distractors semantic effects preceded phonological effects whereas with visual distractors phonological effects had an earlier onset than semantic effects. Experiment 2 provided a means for accounting for this discrepancy by demonstrating that the results for visual distractors followed the auditory pattern when presentation time was limited. The following two experiments addressed the issue of interactivity vs. modularity in speaking by employing auditory distractors and investigating the effects of complex types of distractors. Experiment 3 factorially crossed the factors of semantic and phonological relatedness by employing both semantically and phonologically related distractors (FLY-FLEA). An interaction between the two factors was obtained which was interpreted as supporting an interactive account of speaking. Experiment 4 investigated the effects of mediated distractors which are related to the picture name via an intervening word (TIDE-(TIGER)-LION). A potential effect of such distractors would require an interplay between semantic and phonological levels and thus further support an interactive view. The results showed no effects on naming latencies, a finding that probably is not diagnostic with regard to the question of interactive vs. modular accounts. The second part of this thesis introduced an interactive computational model closely related to Dell's (1986) model of speech production. This model yielded a sequence of semantic and phonological effects and showed an interaction between the two factors as well as the absence of mediated effects. In summary, the experiments and the model favor an interactive view of speaking in which semantic and phonological levels are closely interconnected.