Abstract: One of the workhorses in studying spoken word production is the picture-word interference paradigm (PWI). In this paradigm, speakers are instructed to ignore superimposed written distractor words while fulfilling the picture-naming task. An essential finding in picture - word interference paradigm is that people spend more time in naming pictures when distractor word is of the same semantic category as the picture naming (semantic related word) than when the distractor is unrelated. That effect is often referred to as “semantic interference effect (SIE)”. A reversed finding is that pictures naming latency is shorter in condition of semantic related words than in condition of unrelated words. That effect is referred to as “semantic facilitation effect”. At present, there are several theories about the nature and level of semantic effects in picture - word interference paradigm. Lexical selection by competition hypothesis assumes that SIE is the result of competition between the representations of semantic related distractor word and the target word and then arises at lexical level. Conceptual selection model interprets the semantic effects as the result of competition between the representations of distractor conception and the target conception. As a result, semantic effect should arise at semantic level. Response selection account proposes that there is a single-channel output buffer in word production and the non –target response would occupy the buffer earlier than the target. It will take some time to exclude the non-target response from the buffer and induces SIE. So SIE arises at the post-lexical stage in word production. Each account has its experimental evidence and each has its difficulty in explaining some semantic phenomenon. In the present study, 2 experiments were conducted to investigate the universality of current semantic theories and to explore the roles of semantic similarity and category size on semantic effect in PWI. In Experiment 1, subjects were asked to name pictures accompanied by words with high semantic similarity or words with low semantic similarity at either basic level or at category level. Results showed a shorter picture - naming latency in condition of high semantic similarity distractor words than in condition of low semantic similarity words, leading to significant semantic similarity effect. Nevertheless, semantic similarity effect occurred in basic - level naming rather than in category - level naming and the effect was stronger for low familiar pictures than for high familiar ones. Experiment 1 also showed that latency of category - level naming was shorter than that of basic-level naming and high familiar pictures were named faster than low familiar ones. Combining previous studies, these results suggested that the intensity of semantic relationship between pictures and words would affect the direction of semantic effect in the PWI. Semantic facilitation effect will be found when there is strong semantic relationship between pictures and words. Otherwise, semantic interference will be found. In Experiment 2, subjects were asked to name pictures accompanied by semantic related words or by unrelated words. Thirty pictures from large size of category and another thirty pictures from small size of category were chosen for this experiment. Results showed that semantic related words had rather different influences on pictures naming in different condition. They would promote pictures category-level naming, thus giving rise to semantic facilitation effect. However, they would interference pictures basic-level naming, thus causing semantic interference effect. Category size had a prominent influence on these semantic effects. Semantic interference effect would be stronger for large size of category pictures in basic-level naming and semantic facilitation effect also would be stronger for big size of category pictures in category-level naming. Combining previous studies, the experiment suggested that the range of semantic relationship between pictures and words affects the size of semantic effect. When there is wide range of semantic relationship, the semantic effect will became stronger. Otherwise, the semantic effect will be weaker. Single current theory of semantic effect couldn’t give a proper explanation for the findings in this study. Results in this study were discussed with reference to the equilibrium between conceptual priming and lexical competition. If the conceptual priming overweight the lexical competition, semantic facilitation effect would be found, otherwise semantic interference would be found.

Key words: semantic similarity, category size, picture-word interference paradigm, semantic effect