Two picture-word interference experiments are reported in which the boundaries of the semantic interference effect are explored. In both experiments, participants named pictures (e.g., a picture of a car) that appeared with superimposed word distractors. Distractor words from the same semantic category as the word for the picture (e.g., CAE) produced semantic interference, whereas semantically related distractors from a different category (e.g., BUMPER) led to semantic facilitation. In Experiment 2, the semantic facilitation from semantically related distractors was replicated. These results indicate that a semantic relationship between picture and distractor does not necessarily lead to interference and in fact can lead to facilitation. In all but one case tested until now, a semantic relationship between picture and distractor has led to semantic facilitation. The implications of these results for the assumption that the semantic interference effect arises as a consequence of lexical competition are discussed.
The picture-word interference paradigm, in which participants name pictures while ignoring distractor words, has been used to inform both theories of attention and theories of language production (see, e.g., MacLeod, 1991, for an overview). A well established effect in this paradigm is the semantic interference effect (SIE): When the distractor word and the picture belong to the same semantic category (e.g., CAT, dog), naming latencies are longer than when they are unrelated (e.g., MAT, dog; see, Glaser & Dungelhoff, 1984; Glaser & Glaser, 1989; La Heij, 1988; Lupker, 1979; Rosinski, 1977).1 In the context of language production research, the SIE has been interpreted as supporting the assumption of lexical selection by competition (see, e.g., Roelofs, 1992; Schriefers, Meyer, & Levelt, 1990). Here, we evaluate such an interpretation and bring experimental data that help to understand the origin of the SIE.
Many models of lexical access assume that the ease with which a lexical node is selected depends not only on its level of activation but also on that of other lexical nodes (e.g., Costa & Caramazza, 2002; Roelofs, 1992; Starreveld & La Heij, 1995). If at the time of selection other lexical nodes are highly activated, selection of the target lexical node will be delayed. The SIE is assumed to reveal the greater lexical competition produced by related than by unrelated distractors. Related distractors interfere more because they are, hypothetically, more activated than unrelated distractors. This differential level of activation arises because the picture's semantic representation (dog) activates the lexical node of the related distractor (CAT) but not that of the unrelated distractor (MAT; see Roelofs, 1992). As a result, the activation level of the lexical node CAT is higher (i.e., it receives activation from two sources: the picture's semantic representation and the distractor presentation) than that of the distractor MAT (which receives activation from one source only: the distractor presentation), which makes the former a stronger competitor than the latter.
However, there are three observations that are problematic for the interpretation of the SIE in terms of lexical selection by competition. First, if part of the interference produced by a distractor is due to lexical competition, then lexical nodes with relatively low levels of activation (low-frequency words) should interfere less than those with higher levels of activation (high-frequency words). However, this is not the case; low-frequency distractors interfere more than high-frequency distractors do (Miozzo & Caramazza, 2003).
Second, if the SIE reflects lexical competition, then it should not be present when verbal responses are not necessary. However, semantic interference (SI) has been observed for manual responses (Lupker & Katz, 1981; but see Schriefers et al., 1990).
Third, of special interest in the present context is the observation that a semantic relationship between target and distractors does not always lead to SI. …