Publications

Abstract

Spoken words are highly variable and therefore listeners interpret speech sounds relative to the surrounding acoustic context, such as the speech rate of a preceding sentence. For instance, a vowel midway between short /ɑ/ and long /a:/ in Dutch is perceived as short /ɑ/ in the context of preceding slow speech, but as long /a:/ if preceded by a fast context. Despite the well-established influence of visual articulatory cues on speech comprehension, it remains unclear whether visual cues to speech rate also influence subsequent spoken word recognition. In two ‘Go Fish’-like experiments, participants were presented with audio-only (auditory speech + fixation cross), visual-only (mute videos of talking head), and audiovisual (speech + videos) context sentences, followed by ambiguous target words containing vowels midway between short /ɑ/ and long /a:/. In Experiment 1, target words were always presented auditorily, without visual articulatory cues. Although the audio-only and audiovisual contexts induced a rate effect (i.e., more long /a:/ responses after fast contexts), the visual-only condition did not. When, in Experiment 2, target words were presented audiovisually, rate effects were observed in all three conditions, including visual-only. This suggests that visual cues to speech rate in a context sentence influence the perception of following visual target cues (e.g., duration of lip aperture), which at an audiovisual integration stage bias participants’ target categorization responses. These findings contribute to a better understanding of how what we see influences what we hear.

Abstract

When learning a second spoken language, cognates, words overlapping in form and meaning with one’s native language, help breaking into the language one wishes to acquire. But what happens when the to-be-acquired second language is a sign language? We tested whether hearing nonsigners rely on their gestural repertoire at first exposure to a sign language. Participants saw iconic signs with high and low overlap with the form of iconic gestures while electrophysiological brain activity was recorded. Upon first exposure, signs with low overlap with gestures elicited enhanced positive amplitude in the P3a component compared to signs with high overlap. This effect disappeared after a training session. We conclude that nonsigners generate expectations about the form of iconic signs never seen before based on their implicit knowledge of gestures, even without having to produce them. Learners thus draw from any available semiotic resources when acquiring a second language, and not only from their linguistic experience

Abstract

Perhaps the main advantage of being bilingual is the capacity to communicate with interlocutors that have different language backgrounds. In the life of a bilingual, switching interlocutors hence sometimes involves switching languages. We know that the capacity to switch from one language to another is supported by control mechanisms, such as task-set reconfiguration. This study investigates whether similar neurophysiological mechanisms support bilingual switching between different listeners, within and across languages. A group of 48 unbalanced Dutch-English bilinguals named pictures for two monolingual Dutch and two monolingual English life-size virtual listeners in an immersive virtual reality environment. In terms of reaction times, switching languages came at a cost over and above the significant cost of switching from one listener to another. Analysis of event-related potentials showed similar electrophysiological correlates for switching listeners and switching languages. However, it was found that having to switch listeners and languages at the same time delays the onset of lexical processes more than a switch between listeners within the same language. Findings are interpreted in light of the interplay between proactive (sustained inhibition) and reactive (task-set reconfiguration) control in bilingual speech production. It is argued that a possible bilingual advantage in executive control may not be due to the process of switching per se. This study paves the way for the study of bilingual language switching in ecologically valid, naturalistic, experimental settings.

Abstract

To test the BIA+ and Multilink models’ accounts of how bilinguals process words with different degrees of cross-linguistic orthographic and semantic overlap, we conducted two experiments manipulating stimulus list composition. Dutch-English late bilinguals performed two English lexical decision tasks including the same set of cognates, interlingual homographs, English control words, and pseudowords. In one task, half of the pseudowords were replaced with Dutch words, requiring a ‘no’ response. This change from pure to mixed language list context was found to turn cognate facilitation effects into inhibition. Relative to control words, larger effects were found for cognate pairs with an increasing cross-linguistic form overlap. Identical cognates produced considerably larger effects than non-identical cognates, supporting their special status in the bilingual lexicon. Response patterns for different item types are accounted for in terms of the items’ lexical representation and their binding to ‘yes’ and ‘no’ responses in pure vs mixed lexical decision.

Abstract

In everyday human communication, we often express our communicative intentions by manually pointing out referents in the material world around us to an addressee, often in tight synchronization with referential speech. This study investigated whether and how the kinematic form of index finger pointing gestures is shaped by the gesturer's communicative intentions and how this is modulated by the presence of concurrently produced speech. Furthermore, we explored the neural mechanisms underpinning the planning of communicative pointing gestures and speech. Two experiments were carried out in which participants pointed at referents for an addressee while the informativeness of their gestures and speech was varied. Kinematic and electrophysiological data were recorded online. It was found that participants prolonged the duration of the stroke and poststroke hold phase of their gesture to be more communicative, in particular when the gesture was carrying the main informational burden in their multimodal utterance. Frontal and P300 effects in the ERPs suggested the importance of intentional and modality-independent attentional mechanisms during the planning phase of informative pointing gestures. These findings contribute to a better understanding of the complex interplay between action, attention, intention, and language in the production of pointing gestures, a communicative act core to human interaction.

Abstract

A fundamental property of language is that it can be used to refer to entities in the extra-linguistic physical context of a conversation in order to establish a joint focus of attention on a referent. Typological and psycholinguistic work across a wide range of languages has put forward at least two different theoretical views on demonstrative reference. Here we contrasted and tested these two accounts by investigating the electrophysiological brain activity underlying the construction of indexical meaning in comprehension. In two EEG experiments, participants watched pictures of a speaker who referred to one of two objects using speech and an index-finger pointing gesture. In contrast with separately collected native speakers’ linguistic intuitions, N400 effects showed a preference for a proximal demonstrative when speaker and addressee were in a face-to-face orientation and all possible referents were located in the shared space between them, irrespective of the physical proximity of the referent to the speaker. These findings reject egocentric proximity-based accounts of demonstrative reference, support a sociocentric approach to deixis, suggest that interlocutors construe a shared space during conversation, and imply that the psychological proximity of a referent may be more important than its physical proximity.

Abstract

Comprehension of pointing gestures is fundamental to human communication. However, the neural mechanisms
that subserve the integration of pointing gestures and speech in visual contexts in comprehension
are unclear. Here we present the results of an fMRI study in which participants watched images of an
actor pointing at an object while they listened to her referential speech. The use of a mismatch paradigm
revealed that the semantic unication of pointing gesture and speech in a triadic context recruits left
inferior frontal gyrus. Complementing previous ndings, this suggests that left inferior frontal gyrus
semantically integrates information across modalities and semiotic domains.

Abstract

We examined language-switching effects in French–English bilinguals using a paradigm where pictures are always named in the same language (either French or English) within a block of trials, and on each trial, the picture is preceded by a printed word from the same language or from the other language. Participants had to either make a language decision on the word or categorize it as an animal name or not. Picture-naming latencies in French (Language 1 [L1]) were slower when pictures were preceded by an English word than by a French word, independently of the task performed on the word. There were no language-switching effects when pictures were named in English (L2). This pattern replicates asymmetrical switch costs found with the cued picture-naming paradigm and shows that the asymmetrical pattern can be obtained (a) in the absence of artificial (nonlinguistic) language cues, (b) when the switch involves a shift from comprehension in 1 language to production in another, and (c) when the naming language is blocked (univalent response). We concluded that language switch costs in bilinguals cannot be reduced to effects driven by task control or response-selection mechanisms.

Abstract

Did one of your parents, siblings, or friends ever tell you that you were talking in your sleep? Nothing to be ashamed of! A recent study found that more than half of all people have had the experience of speaking out loud while being asleep [1]. This might even be underestimated, because often people do not notice that they are sleep-talking, unless somebody wakes them up or tells them the next day. Most neuroscientists, linguists, and psychologists studying language are interested in our language production and language comprehension skills during the day. In the present article, we will explore what is known about the production of overt speech during the night. We suggest that the study of sleep-talking may be just as interesting and informative as the study of wakeful speech.