Publications

Abstract

We investigated the time course of conjunctive ''same''-''different'' judgements for visually presented object pairs by means of combined reaction time and on-line eye movement measurements. The analyses of viewing patterns, viewing times, and reaction times showed that participants engaged in a parallel self-terminating search for differences. In addition, the results obtained for objects differing in only one dimension suggest that processing times may depend on the relative codability of the stimulus dimensions. The results are reviewed in a broader framework in view of higher-order processes. We propose that overspecifications of colour, often found in object descriptions, may have an ''early'' visual rather than a ''late'' linguistic origin. In a parallel assessment of the detection materials, participants overspecified the objects' colour substantially more often than their size. We argue that referential overspecifications of colour are largely attributable to mechanisms of visual discrimination.

Abstract

The study investigated the neuronal basis of the retrieval of words from the mental lexicon. The semantic category interference effect was used to locate lexical retrieval processes in time and space. This effect reflects the finding that, for overt naming, volunteers are slower when naming pictures out of a sequence of items from the same semantic category than from different categories. Participants named pictures blockwise either in the context of same- or mixedcategory items while the brain response was registered using magnetoencephalography (MEG). Fifteen out of 20 participants showed longer response latencies in the same-category compared to the mixed-category condition. Event-related MEG signals for the participants demonstrating the interference effect were submitted to a current source density (CSD) analysis. As a new approach, a principal component analysis was applied to decompose the grand average CSD distribution into spatial subcomponents (factors). The spatial factor indicating left temporal activity revealed significantly different activation for the same-category compared to the mixedcategory condition in the time window between 150 and 225 msec post picture onset. These findings indicate a major involvement of the left temporal cortex in the semantic interference effect. As this effect has been shown to take place at the level of lexical selection, the data suggest that the left temporal cortex supports processes of lexical retrieval during production.

Abstract

In English, words like scissors are grammatically plural but conceptually singular, while words like suds are both grammatically and conceptually plural. Words like army can be construed plurally, despite being grammatically singular. To explore whether and how congruence between grammatical and conceptual number affected the production of subject-verb number agreement in English, we elicited sentence completions for complex subject noun phrases like The advertisement for the scissors. In these phrases, singular subject nouns were followed by distractor words whose grammatical and conceptual numbers varied. The incidence of plural attraction (the use of plural verbs after plural distractors) increased only when distractors were grammatically plural, and revealed no influence from the distractors' number meanings. Companion experiments in Dutch offered converging support for this account and suggested that similar agreement processes operate in that language. The findings argue for a component of agreement that is sensitive primarily to the grammatical reflections of number. Together with other results, the evidence indicates that the implementation of agreement in languages like English and Dutch involves separable processes of number marking and number morphing, in which number meaning plays different parts.

Abstract

Earlier research has established that speakers usually fixate the objects they name and that the viewing time for an object depends on the time necessary for object recognition and for the retrieval of its name. In three experiments, speakers produced pronouns and noun phrases to refer to new objects and to objects already known. Speakers looked less frequently and for shorter periods at the objects to be named when they had very recently seen or heard of these objects than when the objects were new. Looking rates were higher and viewing times longer in preparation of noun phrases than in preparation of pronouns. If it is assumed that there is a close relationship between eye gaze and visual attention, these results reveal (1) that speakers allocate less visual attention to given objects than to new ones and (2) that they allocate visual attention both less often and for shorter periods to objects they will refer to by a pronoun than to objects they will name in a full noun phrase. The experiments suggest that linguistic processing benefits, directly or indirectly, from allocation of visual attention to the referent object.

Abstract

Recently, a new theory of timing in sentence production has been proposed by Ferreira (1993). This theory assumes that at the phonological level, each syllable of an utterance is assigned one or more abstract timing units depending on its position in the prosodic structure. The number of timing units associated with a syllable determines the time interval between its onset and the onset of the next syllable. An interesting prediction from the theory, which was confirmed in Ferreira's experiments with speakers of American English, is that the time intervals between syllable onsets should only depend on the syllables' positions in the prosodic structure, but not on their segmental content. However, in the present experiments, which were carried out in Dutch, the intervals between syllable onsets were consistently longer for phonetically long syllables than for short syllables. The implications of this result for models of timing in sentence production are discussed.

Abstract

Two experiments examined phonological priming effects on reaction times, error rates, and event-related brain potential (ERP) measures in an auditory lexical decision task. In Experiment 1 related prime-target pairs rhymed, and in Experiment 2 they alliterated (i.e., shared the consonantal onset and vowel). Event-related potentials were recorded in a delayed response task. Reaction times and error rates were obtained both for the delayed and an immediate response task. The behavioral data of Experiment 1 provided evidence for phonological facilitation of word, but not of nonword decisions. The brain potentials were more negative to unrelated than to rhyming word-word pairs between 450 and 700 msec after target onset. This negative enhancement was not present for word-nonword pairs. Thus, the ERP results match the behavioral data. The behavioral data of Experiment 2 provided no evidence for phonological Facilitation. However, between 250 and 450 msec after target onset, i.e., considerably earlier than in Experiment 1, brain potentials were more negative for unrelated than for alliterating word and word-nonword pairs. It is argued that the ERP effects in the two experiments could be modulations of the same underlying component, possibly the N400. The difference in the timing of the effects is likely to be due to the fact that the shared segments in related stimulus pairs appeared in different word positions in the two experiments.