Kristof Strijkers

Language in the dyad: Most research on language and the brain has studied the individual, yet dialogue is the primary form of language use. LaDy aims to link 2 phenomena that capture this joint nature: linguistic alignment in behaviour and neural alignment between brains. Combining EEG hyperscanning with a novel dyadic paradigm, the project tests whether prediction is the mechanism that drives both.

Social interaction is argued to play a crucial role for grounding abstract knowledge, yet empirical evidence is scarce. To investigate whether social interaction affects the processing of abstract words, 60 French speakers semantically categorized the degree of socialness and concreteness of words either individually or in dyads. When judging the socialness of words, dyads showed a processing advantage for abstract social words that was absent in individual performance. In contrast, when judging the concreteness of words, dyads were less accurate for abstract social words than individuals, confirming that social interaction renders these words more concrete. Dividing the dyads by their level of social engagement based on gaze patterns revealed that the effects were driven by the more cooperative dyads. The findings demonstrate that language processing is distinct between interactive and isolated contexts, where social interaction and engagement dynamically shape the interpretation of abstract concepts.

It remains debated whether language comprehension and production rely on shared or modality-specific mechanisms, and whether phonological, semantic, and pragmatic information is accessed sequentially (with opposite orders across modalities) or in parallel. EEG was recorded in healthy native German speakers in a fully crossed design, contrasting comprehension (written words) with production (picture naming) and varying pragmatic function (naming vs. requesting), semantic category (tools vs. animals), and word-initial phonology (place of articulation: labial vs. coronal). ERPs showed an ultra-early main effect of modality at ∼100 msec with no interaction with the three linguistic factors, consistent with perceptual differences between written words and pictures. More importantly, between 100 and 200 msec, ERPs showed a three-way interaction of the factors pragmatics, semantics, and phonology without modality involvement, indicating early modality-independent linguistic processing. In 100- to 200-msec source estimates, no significant PoA-specific clusters were observed, likely due to limited spatial resolution for focal articulatory contrasts. By contrast, pragmatics and semantics showed significant effects: Activity was greater in prefrontal-motor regions for requesting versus naming and for tools versus animals, whereas posterior visual regions showed greater activity for naming versus requesting and for animals versus tools, supporting an early neural signature of pragmatic and semantic processing that was statistically indistinguishable between the two modalities. Modality first entered the effects only at ∼400 msec, possibly reflecting earlier decay in comprehension versus sustained activation for utterance generation in production. Overall, results support parallel, modality-general processing underlying both language comprehension and production.

Social interaction is argued to play a crucial role for grounding abstract knowledge, yet empirical evidence is scarce. To investigate whether social interaction affects the processing of abstract words, sixty French speakers semantically categorized the degree of socialness and concreteness of words either individually or in dyads. When judging the socialness of words, dyads showed a processing advantage for abstract social words that was absent in individual performance. In contrast, when judging the concreteness of words, dyads were less accurate for abstract social words than individuals, confirming that social interaction renders these words more concrete. Dividing the dyads by their level of social engagement based on mutual gaze patterns, revealed that the effects were driven by the more cooperative dyads. The findings demonstrate that language processing differs fundamentally between interactive and isolated contexts, where social interaction and engagement dynamically shape the interpretation of abstract concepts.

This study investigated the role of meaning prediction in dyadic interactions. Participants engaged in a semantic association game in which the predictability of upcoming word categories was manipulated. Results showed that predictability speeds up speech production in both interlocutors. Critically, our study reveals that meaning prediction not only aids language comprehension and subsequent speech production for the interlocutor completing a predictable sentence but enhances even more the response speed of the conversational partner formulating a reply. This result demonstrated an incremental dyadic prediction effect during language interaction. A control experiment in which participants performed the same task but in isolation confirmed that this effect is entirely driven by the interactive context. While participants showed a similar facilitation effect when completing predictable sentences as in the dyadic experiment, the prediction effect for formulating a reply disappeared. These findings reveal fundamental differences in predictive and linguistic processing during communicative interactions versus individual language use. They provide strong empirical support for theories of joint action and dialog, which emphasize that successful social interaction relies on predicting and representing the linguistic information of both conversational partners. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

In this functional magnetic resonance imaging study, we investigated whether language production and understanding recruit similar phoneme-specific networks. We did so by comparing the brain’s response to different phoneme categories in minimal pairs: Bilabial-initial words (eg “monkey”) were contrasted to alveolar-initial words (eg “donkey”) in 37 participants performing both language production and comprehension tasks. Individual-specific region-of-interest analyses showed that the same sensorimotor networks were activated across the language modalities. In motor regions, word production and comprehension elicited the same phoneme-specific topographical activity patterns, with stronger haemodynamic activations for alveolar-initial words in the tongue cortex and stronger activations for bilabial-initial words in the lip cortex. In the posterior and middle superior temporal cortex, production and comprehension likewise resulted in similar activity patterns, with enhanced activations to alveolar- compared to bilabial-initial words. These results disagree with the classical asymmetry between language production and understanding in neurobiological models of language, and instead advocate for a cortical organization where phonology is carried by similar topographical activations in motor cortex and distributed activations in temporal cortex across the language modalities.

This study investigates the role of meaning prediction in dyadic interactions. Participants engaged in a semantic association game in which the predictability of upcoming word categories was manipulated. Results showed that predictability speeds up speech production in both interlocutors. Critically, our study reveals that meaning prediction not only aids language comprehension and subsequent speech production for the interlocutor completing a predictable sentence but enhances even more the response speed of the conversational partner formulating a reply. This result demonstrates an incremental dyadic prediction effect during language interaction. A control experiment in which participants performed the same task but in isolation confirmed that this effect is entirely driven by the interactive context. While participants showed a similar facilitation effect when completing predictable sentences as in the dyadic experiment, the prediction effect for formulating a reply disappeared. These findings reveal fundamental differences in predictive and linguistic processing during communicative interactions versus individual language use. They provide strong empirical support for theories of joint action and dialogue, which emphasize that successful social interaction relies on predicting and representing the linguistic information of both conversational partners.

Words challenge embodied cognition theories due to their lack of direct connections to the sensory and bodily world. To address this, some theories propose that abstract words are represented through emotional and social information. We tested these theories across seven experiments using semantic categorization and lexical decision tasks in two languages. In Experiment 1, we investigated the effects of emotional valence, socialness and sensory experience in a large-scale study using a lexical decision task. We found that positive valence and socialness facilitates word recognition. In Experiment 2, we explored socialness and its interaction with concreteness in two semantic categorization tasks in English and French. While concreteness consistently facilitated word recognition, the effects of socialness varied across languages. In Experiment 3, we used the same tasks to investigate the effects of emotional valence, showing that valence facilitated abstract word recognition in both languages, but only if the task required decisions about valence. In Experiments 4-7, we primed lexical decision and semantic categorization of target words by social or affective primes. Affective priming enhanced the valence effect, whereas socialness priming did not enhance the socialness effects. Overall, our data provide evidence that emotional valence plays a strategic role in the processing of abstract words, while socialness does not seem to influence the processing of abstract words. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

The motor system is known to process temporal information, and moving rhythmically while listening to a melody can improve auditory processing. In three interrelated behavioural experiments, we demonstrate that this effect translates to speech processing. Motor priming improves the efficiency of subsequent naturalistic speech-in-noise processing under specific conditions. (i) Moving rhythmically at the lexical rate (~1.8 Hz) significantly improves subsequent speech processing compared to moving at other rates, such as the phrasal or syllabic rates. (ii) The impact of such rhythmic motor priming is not influenced by whether it is self-generated or triggered by an auditory beat. (iii) Overt lexical vocalization, regardless of its semantic content, also enhances the efficiency of subsequent speech processing. These findings provide evidence for the functional role of the motor system in processing the temporal dynamics of naturalistic speech.

This study aimed to assess the extent to which human participants co-represent the lexico-semantic processing of a humanoid robot partner. Specifically, we investigated whether participants would engage their speech production system to predict the robot’s upcoming words, and how they would progressively adapt to the robot’s verbal behaviour. In the experiment, a human participant and a robot alternated in naming pictures of objects from 15 semantic categories, while the participant’s electrophysiological activity was recorded. We manipulated word frequency as a measure of lexical access, with half of the pictures associated with high-frequency names and the other half with low-frequency names. In addition, the robot was programmed to provide semantic category labels (e.g., “tool” for the picture of a hammer) instead of the more typical basic-level names (e.g., “hammer”) for items in five categories. Analysis of the stimulus-locked activity revealed a comparable event-related potential (ERP) associated with word frequency both when it was the participant’s and the robot’s turn to speak. Analysis of the response-locked activity showed a different pattern for the category and basic-level responses in the first but not in the second part of the experiment, suggesting that participants adapted to the robot’s lexico-semantic patterns over time. These findings provide empirical evidence for two key points: (1) participants engage their speech production system to predict the robot’s upcoming words and (2) partner-adaptive behaviour facilitates comprehension of the robot’s speech.