The effects of a concomitant distractor on word reading aloud and picture naming tasks

The aim of this thesis was to investigate properties of the human reading and speech production systems using picture naming or word reading tasks in four paradigms, all involving to-be-ignored distractors: 1) Picture-Nonword Interference, PNWI 2) Picture-Word Interference, PWI 3) Word-Word Interference, WWI 4) Word-Nonword Interference, WNWI. The dual route theory of reading was the theoretical framework for discussing the results. Human data and DRC simulations, using a new Semantic version of the DRC model, are reported. Paper 1 of the thesis investigated the effects of nonword distractor length, target length, and initial and final target-distractor phonological relatedness on the PNWI effect. Furthermore, it reports the first attempt in the psycholinguistic literature to disambiguate between the role of the number of phonemes or the number of syllables in the nonword distractor length effect observed in PNWI. Paper 2 explored the role of target picture frequency on the PNWI and PWI effects. Comparisons between human data and simulations led to the suggestion that the phoneme level of the human system possesses a relative-position coding scheme rather than the absolute-position coding scheme postulated by the DRC model. Paper 3 used the WWI and WNWI paradigms to investigate the interplay between the lexical and nonlexical routes by varying nonword distractor length, nonword distractor pronounceability and word target frequency. Overall the results reported in the thesis emphasize the interplay between the lexical, nonlexical and semantic routes together with the inability of the human speech production and reading system to ignore the distractors in these four paradigms. More importantly the results demonstrate that in the human speech production system position coding at the phoneme level does not use an absolute-position coding scheme.