Semantic Effects in Speech Production

Semantic Effects in Speech Production Adrian Nestor (adriannestor@students.nbu.bg) Elena Andonova (eandonova@cogs.nbu.bg) Department of Cognitive Science New Bulgarian University, 21, Montevideo Street Sofia 1618, Bulgaria Abstract The paper reports empirical and computational research on semantic facilitation and inhibition in the picture-word interference paradigm for different values of stimulus onset asynchrony (SOA). The main claim it makes is that purely semantic facilitation effects are conditioned by the degree of picture-word semantic similarity in contrast to inhibition effects for which categorical relatedness is typically sufficient. The experimental results support this claim and a simulation with an attractor neural network attempts to provide a unified account of semantic facilitation and inhibition in this paradigm as a function of SOA. Introduction Semantic facilitation from context words in a picture naming task, just like semantic priming in visual word recognition, has been a somewhat controversial issue. However, in picture naming, unlike word recognition, the issue does not seem to have been settled in favor of facilitation. It is naturally to ask then why purely semantic facilitation should show up when making a lexical decision or reading words but not when naming pictures. Both methodological and theoretical grounds are examined as potentially responsible for the failure to establish such a result with a picture naming task. The claim we attempt to support is that the categorical view on semantic similarity, as opposed to a graded featural one, is mainly responsible here. However, if facilitation is shown to be possible, one has to face the challenge of accommodating it with other experimental results, notably picture-word interference, in the framework of a general theory of speech production. Originating with the study of Rosinski, Golinkoff & Kukish (1975), the picture-word interference paradigm established a classical result in the psycholinguistic literature. To put it succinctly, it takes more time to name the picture of an object in the presence of a semantically related word than in the presence of an unrelated one. For instance, naming the picture of a DOG in the presence of the word ‘cat’ takes longer than in the presence of ‘tree’. The classical study of Glaser and Dungelhoff (1984) opened the way to time-course analyses of the interference effect in the picture-word paradigm by systematic manipulation of the stimulus onset asynchrony (SOA) values, i.e. the temporal difference between the onsets of the two stimuli on a trial, the target picture and the context word. Examining different SOA values ranging from –400 to 400 ms, where negative SOA values correspond to word onset preceding picture onset, the two researchers found semantic inhibition in a small time window around synchrony (SOA=0) with a maximum inhibitory effect at 100 SOA. A facilitation effect at – 400 ms SOA, on the other hand, was not found to be significant. Semantic interference around synchrony has been replicated many times and extended to cover various modifications of stimulus properties such as modality of the prime, category of named objects, stimulus duration, SOA etc. (Alario, Segui & Ferrand, 2000; Damian & Martin, 1999; La Heij, 1988; Roelofs, 1992; Schriefers, Meyer & Levelt, 1990; Starreveld & La Heij, 1996). Facilitation at early SOAs, on the other hand, was more of a debated possibility. While the early studies of Sperber, McCauley, Ragain and Weil (1979) and Carr, McCauley, Sperber and Parmelee (1982) reported facilitation, later research failed to obtain it (Alario, Segui & Ferrand, 2000; Glaser & Glaser, 1989; La Heij, Dirx & Kramer, 1990). The reason invoked for this difference was twofold. First, early studies used long or very long SOAs – Sperber et al. (1979), for instance, reported facilitation for an interstimulus interval of as much as one second – which opened the gate to strategies on the part of subjects. Second, they failed to separate semantic from associative relatedness. ‘Dog’ and ‘cat’, for example, are good candidates not only for cohyponims, i.e. members of the same semantic category, but also for close associates as recorded by free association norms. The nature of the facilitation could have been then associative rather than semantic as suggested by robust purely associative facilitation results at negative SOA values (Alario, Segui & Ferrand, 2000; La Heij, Dirx & Kramer, 1990; Lupker, 1988). As a result, currently the issue seems to be settled pretty much against the possibility of purely semantic facilitation at negative SOAs. The debate on facilitation in the picture-word paradigm can be paralleled quite interestingly with the debate on automatic semantic priming in lexical decision and word reading. Does a word prime speed up, for instance, the lexical decision for a semantically related word compared to a semantically unrelated one? The examination of many studies investigating this issue cannot give us a straight answer (see Neely, 1991 for a review). Similarly to the line taken in the picture-word paradigm, it was suggested that automatic priming in such a task reflects only an associative relationship (Shelton & Martin, 1992). McRae and Boisvert (1998) suggested that the divergence of results and the failure to elicit purely semantic priming in