The influence of speaker gaze on listener comprehension: Contrasting visual versus intentional accounts

When a look is enough: Neurophysiological correlates of referential speaker gaze in situated comprehension

Behavioral studies have shown that speaker gaze to objects in a co-present scene can influence listeners' expectations about how the utterance will unfold. These findings have recently been supported by ERP studies that linked the underlying mechanisms of the integration of speaker gaze with an utterance meaning representation to multiple ERP components. This leads to the question, however, as to whether speaker gaze should be considered part of the communicative signal itself, such that the referential information conveyed by gaze can help listeners not only form expectations but also to confirm referential expectations induced by the prior linguistic context. In the current study, we investigated this question by conducting an ERP experiment (N=24, Age:[19,31]), in which referential expectations were established by linguistic context together with several depicted objects in the scene. Those expectations then could be confirmed by subsequent speaker gaze that preceded the referential expression. Participants were presented with a centrally positioned face performing gaze actions aligned to utterances comparing two out of three displayed objects, with the task to judge whether the sentence was true given the provided scene. We manipulated the gaze cue to be either Present (toward the subsequently named object) or Absent preceding contextually Expected or Unexpected referring nouns. The results provided strong evidence for gaze as being treated as an integral part of the communicative signal: While in the absence of gaze, effects of phonological verification (PMN), word meaning retrieval (N400) and sentence meaning integration/evaluation (P600) were found on the unexpected noun, in the presence of gaze effects of retrieval (N400) and integration/evaluation (P300) were solely found in response to the pre-referent gaze cue when it was directed toward the unexpected referent with attenuated effects on the following referring noun.

Influence of Actor's Congruent and Incongruent Gaze on Language Processing

In interpreting spoken sentences in event contexts, comprehenders both integrate their current interpretation of language with the recent past (e.g., events they have witnessed) and develop expectations about future event possibilities. Tense cues can disambiguate this linking but temporary ambiguity in their interpretation may lead comprehenders to also rely on further, situation-specific cues (e.g., an actor's gaze as a cue to his future actions). How comprehenders reconcile these different cues in real time is an open issue that we must address to accommodate comprehension. It has been suggested that relating a referential expression (e.g., a verb) to a referent (e.g., a recent event) is preferred over relying on other cues that refer to the future and are not yet referentially grounded (“recent-event preference”). Two visual-world eye-tracking experiments compared this recent-event preference with effects of an actor's gaze and of tense/temporal adverbs as cues to a future action event. The results revealed that people overall preferred to focus on the recent (vs. future) event target in their interpretation, suggesting that while a congruent and incongruent actor gaze can jointly with futuric linguistic cues neutralize the recent-event preference late in the sentence, the latter still plays a key role in shaping participants' initial verb-based event interpretation. Additional post-experimental memory tests provided insight into the longevity of the gaze effects.

Anticipating a future versus integrating a recent event? Evidence from eye-tracking

When comprehending a spoken sentence that refers to a visually-presented event, comprehenders both integrate their current interpretation of language with the recent event and develop expectations about future event possibilities. Tense cues can disambiguate this linking, but temporary ambiguity in these cues may lead comprehenders to also rely on further, experience-based (e.g., frequency or an actor's gaze) cues. How comprehenders reconcile these different cues in real time is an open issue. Extant results suggest that comprehenders preferentially relate their unfolding interpretation to a recent event by inspecting its target object. We investigated to what extent this recent-event preference could be overridden by short-term experiential and situation-specific cues. In Experiments 1-2 participants saw substantially more future than recent events and listened to more sentences about future-events (75% in Experiment 1 and 88% in Experiment 2). Experiment 3 cued future target objects and event possibilities via an actor's gaze. The event frequency increase yielded a reduction in the recent event inspection preference early during sentence processing in Experiments 1-2 compared with Experiment 3 (where event frequency and utterance tense were balanced) but did not eliminate the overall recent-event preference. Actor gaze also modulated the recent-event preference, and jointly with future tense led to its reversal in Experiment 3. However, our results showed that people overall preferred to focus on recent (vs. future) events in their interpretation, suggesting that while two cues (actor gaze and short-term event frequency) can partially override the recent-event preference, the latter still plays a key role in shaping participants' interpretation.

Multimodal Language Processing in Human Communication

The natural ecology of human language is face-to-face interaction comprising the exchange of a plethora of multimodal signals. Trying to understand the psycholinguistic processing of language in its natural niche raises new issues, first and foremost the binding of multiple, temporally offset signals under tight time constraints posed by a turn-taking system. This might be expected to overload and slow our cognitive system, but the reverse is in fact the case. We propose cognitive mechanisms that may explain this phenomenon and call for a multimodal, situated psycholinguistic framework to unravel the full complexities of human language processing.

Influence of speakers' gaze on situated language comprehension: Evidence from Event-Related Potentials

Behavioral studies have shown that speaker gaze to objects in a co-present scene can influence listeners' sentence comprehension. To gain deeper insight into the mechanisms involved in gaze processing and integration, we conducted two ERP experiments (N = 30, Age: [18, 32] and [19, 33] respectively). Participants watched a centrally positioned face performing gaze actions aligned to utterances comparing two out of three displayed objects. They were asked to judge whether the sentence was true given the provided scene. We manipulated the second gaze cue to be either Congruent (baseline), Incongruent or Averted (Exp1)/Mutual (Exp2). When speaker gaze is used to form lexical expectations about upcoming referents, we found an attenuated N200 when phonological information confirms these expectations (Congruent). Similarly, we observed attenuated N400 amplitudes when gaze-cued expectations (Congruent) facilitate lexical retrieval. Crucially, only a violation of gaze-cued lexical expectations (Incongruent) leads to a P600 effect, suggesting the necessity to revise the mental representation of the situation. Our results support the hypothesis that gaze is utilized above and beyond simply enhancing a cued object's prominence. Rather, gaze to objects leads to their integration into the mental representation of the situation before they are mentioned.

Eye'll Help You Out! How the Gaze Cue Reduces the Cognitive Load Required for Reference Processing

Referential gaze has been shown to benefit language processing in situated communication in terms of shifting visual attention and leading to shorter reaction times on subsequent tasks. The present study simultaneously assessed both visual attention and, importantly, the immediate cognitive load induced at different stages of sentence processing. We aimed to examine the dynamics of combining visual and linguistic information in creating anticipation for a specific object and the effect this has on language processing. We report evidence from three visual‐world eye‐tracking experiments, showing that referential gaze leads to a shift in visual attention toward the cued object, which consequently lowers the effort required for processing the linguistic reference. Importantly, perceiving and following the gaze cue did not prove costly in terms of cognitive effort, unless the cued object did not fit the verb selectional preferences.

Distinct effects of different visual cues on sentence comprehension and later recall: The case of speaker gaze versus depicted actions

Language-processing accounts are beginning to accommodate different visual context effects, but they remain underspecified regarding differences between cues, both during sentence comprehension and subsequent recall. We monitored participants' eye movements to mentioned characters while they listened to transitive sentences. We varied whether speaker gaze, a depicted action, neither, or both of these visual cues were available, as well as whether both cues were deictic (Experiment 1) or only speaker gaze (Experiment 2). Speaker gaze affected eye movements during comprehension similarly early to a single deictic action depiction, but significantly earlier than non-deictic action depictions; conversely, depicted actions but not speaker gaze positively affected later recall of sentence content. Thus, cue type and cue-language relations must be accommodated in characterising real-time situated language comprehension and subsequent recall of sentence content.

Extending Situated Language Comprehension (Accounts) with Speaker and Comprehender Characteristics: Toward Socially Situated Interpretation

More and more findings suggest a tight temporal coupling between (non-linguistic) socially interpreted context and language processing. Still, real-time language processing accounts remain largely elusive with respect to the influence of biological (e.g., age) and experiential (e.g., world and moral knowledge) comprehender characteristics and the influence of the 'socially interpreted' context, as for instance provided by the speaker. This context could include actions, facial expressions, a speaker's voice or gaze, and gestures among others. We review findings from social psychology, sociolinguistics and psycholinguistics to highlight the relevance of (the interplay between) the socially interpreted context and comprehender characteristics for language processing. The review informs the extension of an extant real-time processing account (already featuring a coordinated interplay between language comprehension and the non-linguistic visual context) with a variable ('ProCom') that captures characteristics of the language user and with a first approximation of the comprehender's speaker representation. Extending the CIA to the sCIA (social Coordinated Interplay Account) is the first step toward a real-time language comprehension account which might eventually accommodate the socially situated communicative interplay between comprehenders and speakers.

Perceiving where another person is looking: the integration of head and body information in estimating another person's gaze

The process through which an observer allocates his/her attention based on the attention of another person is known as joint attention. To be able to do this, the observer effectively has to compute where the other person is looking. It has been shown that observers integrate information from the head and the eyes to determine the gaze of another person. Most studies have documented that observers show a bias called the overshoot effect when eyes and head are misaligned. That is, when the head is not oriented straight to the observer, perceived gaze direction is sometimes shifted in the direction opposite to the head turn. The present study addresses whether body information is also used as a cue to compute perceived gaze direction. In Experiment 1, we observed a similar overshoot effect in both behavioral and saccadic responses when manipulating body orientation. In Experiment 2, we explored whether the overshoot effect was due to observers assuming that the eyes are oriented further than the head when head and body orientation are misaligned. We removed horizontal eye information by presenting the stimulus from a side view. Head orientation was now manipulated in a vertical direction and the overshoot effect was replicated. In summary, this study shows that body orientation is indeed used as a cue to determine where another person is looking.