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.

Predictable Words Are More Likely to Be Omitted in Fragments-Evidence From Production Data.

Instead of a full sentence like Bring me to the university (uttered by the passenger to a taxi driver) speakers often use fragments like To the university to get their message across. So far there is no comprehensive and empirically supported account of why and under which circumstances speakers sometimes prefer a fragment over the corresponding full sentence. We propose an information-theoretic account to model this choice: A speaker chooses the encoding that distributes information most uniformly across the utterance in order to make the most efficient use of the hearer's processing resources (Uniform Information Density, Levy and Jaeger, 2007). Since processing effort is related to the predictability of words (Hale, 2001) our account predicts two effects of word probability on omissions: First, omitting predictable words (which are more easily processed), avoids underutilizing processing resources. Second, inserting words before very unpredictable words distributes otherwise excessively high processing effort more uniformly. We test these predictions with a production study that supports both of these predictions. Our study makes two main contributions: First we develop an empirically motivated and supported account of fragment usage. Second, we extend previous evidence for information-theoretic processing constraints on language in two ways: We find predictability effects on omissions driven by extralinguistic context, whereas previous research mostly focused on effects of local linguistic context. Furthermore, we show that omissions of content words are also subject to information-theoretic well-formedness considerations. Previously, this has been shown mostly for the omission of function words.

The Role of UID for the Usage of Verb Phrase Ellipsis: Psycholinguistic Evidence From Length and Context Effects.

We investigate the underexplored question of when speakers make use of the omission phenomenon verb phrase ellipsis (VPE) in English given that the full form is also available to them. We base the interpretation of our results on the well-established information-theoretic Uniform Information Density (UID) hypothesis: Speakers tend to distribute processing effort uniformly across utterances and avoid regions of low information by omitting redundant material through, e.g., VPE. We investigate the length of the omittable VP and its predictability in context as sources of redundancy which lead to larger or deeper regions of low information and an increased pressure to use ellipsis. We use both naturalness rating and self-paced reading studies in order to link naturalness patterns to potential processing difficulties. For the length effects our rating and reading results support a UID account. Surprisingly, we do not find an effect of the context on the naturalness and the processing of VPE. We suggest that our manipulation might have been too weak or not effective to evidence such an effect.

Reevaluating pragmatic reasoning in language games.

The results of a highly influential study that tested the predictions of the Rational Speech Act (RSA) model suggest that (a) listeners use pragmatic reasoning in one-shot web-based referential communication games despite the artificial, highly constrained, and minimally interactive nature of the task, and (b) that RSA accurately captures this behavior. In this work, we reevaluate the contribution of the pragmatic reasoning formalized by RSA in explaining listener behavior by comparing RSA to a baseline literal listener model that is only driven by literal word meaning and the prior probability of referring to an object. Across three experiments we observe only modest evidence of pragmatic behavior in one-shot web-based language games, and only under very limited circumstances. We find that although RSA provides a strong fit to listener responses, it does not perform better than the baseline literal listener model. Our results suggest that while participants playing the role of the Speaker are informative in these one-shot web-based reference games, participants playing the role of the Listener only rarely take this Speaker behavior into account to reason about the intended referent. In addition, we show that RSA's fit is primarily due to a combination of non-pragmatic factors, perhaps the most surprising of which is that in the majority of conditions that are amenable to pragmatic reasoning, RSA (accurately) predicts that listeners will behave non-pragmatically. This leads us to conclude that RSA's strong overall correlation with human behavior in one-shot web-based language games does not reflect listener's pragmatic reasoning about informative speakers.

Graded expectations in visually situated comprehension: Costs and benefits as indexed by the N400.

Recently, Ankener et al. (Frontiers in Psychology, 9, 2387, 2018) presented a visual world study which combined both attention and pupillary measures to demonstrate that anticipating a target results in lower effort to integrate that target (noun). However, they found no indication that the anticipatory processes themselves, i.e., the reduction of uncertainty about upcoming referents, results in processing effort (cf. Linzen and Jaeger, Cognitive Science, 40(6), 1382-1411, 2016). In contrast, Maess et al. (Frontiers in Human Neuroscience, 10, 1-11, 2016) found that more constraining verbs elicited a higher N400 amplitude than unconstraining verbs. The aim of the present study was therefore twofold: Firstly, we examined whether the graded ICA effect, which was previously found on the noun as a result of a likelihood manipulation, replicates in ERP measures. Secondly, we set out to investigate whether the processes leading to the generation of expectations (derived during verb and scene processing) induce an N400 modulation. Our results confirm that visual context is combined with the verb's meaning to establish expectations about upcoming nouns and that these expectations affect the retrieval of the upcoming noun (modulated N400 on the noun). Importantly, however, we find no evidence for different costs in generating more or less specific expectations for upcoming nouns. Thus, the benefits of generating expectations are not associated with any costs in situated language comprehension.

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.

On the predictability of event boundaries in discourse: An ERP investigation.

When reading a text describing an everyday activity, comprehenders build a model of the situation described that includes prior knowledge of the entities, locations, and sequences of actions that typically occur within the event. Previous work has demonstrated that such knowledge guides the processing of incoming information by making event boundaries more or less expected. In the present ERP study, we investigated whether comprehenders' expectations about event boundaries are influenced by how elaborately common events are described in the context. Participants read short stories in which a common activity (e.g., washing the dishes) was described either in brief or in an elaborate manner. The final sentence contained a target word referring to a more predictable action marking a fine event boundary (e.g., drying) or a less predictable action, marking a coarse event boundary (e.g., jogging). The results revealed a larger N400 effect for coarse event boundaries compared to fine event boundaries, but no interaction with description length. Between 600 and 1000 ms, however, elaborate contexts elicited a larger frontal positivity compared to brief contexts. This effect was largely driven by less predictable targets, marking coarse event boundaries. We interpret the P600 effect as indexing the updating of the situation model at event boundaries, consistent with Event Segmentation Theory (EST). The updating process is more demanding with coarse event boundaries, which presumably require the construction of a new situation model.

Teasing apart coercion and surprisal: Evidence from eye-movements and ERPs.

Previous behavioral and electrophysiological studies have presented evidence suggesting that coercion expressions (e.g., began the book) are more difficult to process than control expressions like read the book. While this processing cost has been attributed to a specific coercion operation for recovering an event-sense of the complement (e.g., began reading the book), an alternative view based on the Surprisal Theory of language processing would attribute the cost to the relative unpredictability of the complement noun in the coercion compared to the control condition, with no need to postulate coercion-specific mechanisms. In two experiments, monitoring eye-tracking and event-related potentials (ERPs), respectively, we sought to determine whether there is any evidence for coercion-specific processing cost above-and-beyond the difficulty predicted by surprisal, by contrasting coercing and control expressions with a further control condition in which the predictability of the complement noun was similar to that in the coercion condition (e.g., bought the book). While the eye-tracking study showed significant effects of surprisal and a marginal effect of coercion on late reading measures, the ERP study clearly supported the surprisal account. Overall, our findings suggest that the coercion cost largely reflects the surprisal of the complement noun with coercion specific operations possibly influencing later processing stages.

Processing polarity: how the ungrammatical intrudes on the grammatical.

A central question in online human sentence comprehension is, "How are linguistic relations established between different parts of a sentence?" Previous work has shown that this dependency resolution process can be computationally expensive, but the underlying reasons for this are still unclear. This article argues that dependency resolution is mediated by cue-based retrieval, constrained by independently motivated working memory principles defined in a cognitive architecture. To demonstrate this, this article investigates an unusual instance of dependency resolution, the processing of negative and positive polarity items, and confirms a surprising prediction of the cue-based retrieval model: Partial-cue matches-which constitute a kind of similarity-based interference-can give rise to the intrusion of ungrammatical retrieval candidates, leading to both processing slow-downs and even errors of judgment that take the form of illusions of grammaticality in patently ungrammatical structures. A notable achievement is that good quantitative fits are achieved without adjusting the key model parameters.

Enhancing dominant modes in nonstationary time series by means of the symbolic resonance analysis.

We present the symbolic resonance analysis (SRA) as a viable method for addressing the problem of enhancing a weakly dominant mode in a mixture of impulse responses obtained from a nonlinear dynamical system. We demonstrate this using results from a numerical simulation with Duffing oscillators in different domains of their parameter space, and by analyzing event-related brain potentials (ERPs) from a language processing experiment in German as a representative application. In this paradigm, the averaged ERPs exhibit an N400 followed by a sentence final negativity. Contemporary sentence processing models predict a late positivity (P600) as well. We show that the SRA is able to unveil the P600 evoked by the critical stimuli as a weakly dominant mode from the covering sentence final negativity.

Diagnosis and repair of negative polarity constructions in the light of symbolic resonance analysis.

In a post hoc analysis, we investigate differences in event-related potentials of two studies (Drenhaus et al., 2004, Drenhaus et al., to appear, Saddy et al., 2004a and Saddy et al., 2004b) by using the symbolic resonance analysis (Beim Graben & Kurths, 2003). The studies under discussion, examined the failure to license a negative polarity item (NPI) in German: Saddy et al. (2004a) reported an N400 component when the NPI was not accurately licensed by negation; Drenhaus et al., 2004 and Drenhaus et al., to appear considered additionally the influence of constituency of the licensor in NPI constructions. A biphasic N400-P600 response was found for the two induced violations (the lack of licensor and the inaccessibility of negation in a relative clause). The symbolic resonance analysis (SRA) revealed an effect in the P600 time window for the data in Saddy et al., which was not found by using the averaging technique. The SRA of the ERPs in Drenhaus et al., showed that the P600 components are distinguishable concerning the amplitude and latency. It was smaller and earlier in the condition where the licensor is inaccessible, compared to the condition without negation in the string. Our findings suggest that the failure in licensing NPIs is not exclusively related to semantic integration costs (N400). The elicited P600 components reflect differences in syntactic processing. Our results confirm and replicate the effects of the traditional voltage average analysis and show that the SRA is a useful tool to reveal and pull apart ERP differences which are not evident using the traditional voltage average analysis.

Processing polarity items: contrastive licensing costs.

We describe an experiment that investigated the failure to license polarity items in German using event-related brain potentials (ERPs). The results reveal distinct processing reflexes associated with failure to license positive polarity items in comparison to failure to license negative polarity items. Failure to license both negative and positive polarity items elicited an N400 component reflecting semantic integration cost. Failure to license positive polarity items, however, also elicited a P600 component. The additional P600 in the positive polarity violations may reflect higher processing complexity associated with a negative operator. This difference between the two types of violation suggests that the processing of negative and positive polarity items does not involve identical mechanisms.