The role of systematicity in early referent selection.

Previous studies showed that word learning is affected by children's existing knowledge. For instance, knowledge of semantic category aids word learning, whereas a dense phonological neighbourhood impedes learning of similar-sounding words. Here, we examined to what extent children associate similar-sounding words (e.g., rat and cat) with objects of the same semantic category (e.g., both are animals), that is, to what extent children assume meaning overlap given form overlap between two words. We tested this by first presenting children (N = 93, Mage = 22.4 months) with novel word-object associations. Then, we examined the extent to which children assume that a similar sounding novel label, that is, a phonological neighbour, refers to a similar looking object, that is, a likely semantic neighbour, as opposed to a dissimilar looking object. Were children to preferentially fixate the similar-looking novel object, it would suggest that systematic word form-meaning relations aid referent selection in young children. While we did not find any evidence for such word form-meaning systematicity, we demonstrated that children showed robust learning for the trained novel word-object associations, and were able to discriminate between similar-sounding labels and also similar-looking objects. Thus, we argue that unlike iconicity which appears early in vocabulary development, we find no evidence for systematicity in early referent selection.

Splitting event-related potentials: Modeling latent components using regression-based waveform estimation.

Event-related potentials (ERPs) provide a multidimensional and real-time window into neurocognitive processing. The typical Waveform-based Component Structure (WCS) approach to ERPs assesses the modulation pattern of components-systematic, reoccurring voltage fluctuations reflecting specific computational operations-by looking at mean amplitude in predetermined time-windows. This WCS approach, however, often leads to inconsistent results within as well as across studies. It has been argued that at least some inconsistencies may be reconciled by considering spatiotemporal overlap between components; that is, components may overlap in both space and time, and given their additive nature, this means that the WCS may fail to accurately represent its underlying latent component structure (LCS). We employ regression-based ERP (rERP) estimation to extend traditional approaches with an additional layer of analysis, which enables the explicit modeling of the LCS underlying WCS. To demonstrate its utility, we incrementally derive an rERP analysis of a recent study on language comprehension with seemingly inconsistent WCS-derived results. Analysis of the resultant regression models allows one to derive an explanation for the WCS in terms of how relevant regression predictors combine in space and time, and crucially, how individual predictors may be mapped onto unique components in LCS, revealing how these spatiotemporally overlap in the WCS. We conclude that rERP estimation allows for investigating how scalp-recorded voltages derive from the spatiotemporal combination of experimentally manipulated factors. Moreover, when factors can be uniquely mapped onto components, rERPs may offer explanations for seemingly inconsistent ERP waveforms at the level of their underlying latent component structure.

Event-related potentials index lexical retrieval (N400) and integration (P600) during language comprehension.

The functional interpretation of two salient language-sensitive ERP components - the N400 and the P600 - remains a matter of debate. Prominent alternative accounts link the N400 to processes related to lexical retrieval, semantic integration, or both, while the P600 has been associated with syntactic reanalysis or, alternatively, to semantic integration. The often overlapping predictions of these competing accounts in extant experimental designs, however, has meant that previous findings have failed to clearly decide among them. Here, we present an experiment that directly tests the competing hypotheses using a design that clearly teases apart the retrieval versus integration view of the N400, while also dissociating a syntactic reanalysis/reprocessing account of the P600 from semantic integration. Our findings provide support for an integrated functional interpretation according to which the N400 reflects context-sensitive lexical retrieval - but not integration - processes. While the observed P600 effects were not predicted by any account, we argue that they can be reconciled with the integration view, if spatio-temporal overlap of ERP components is taken into consideration.

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.

The P600 as a continuous index of integration effort.

The integration of word meaning into an unfolding utterance representation is a core operation of incremental language comprehension. There is considerable debate, however, as to which component of the ERP signal-the N400 or the P600-directly reflects integrative processes, with far reaching consequences for the temporal organization and architecture of the comprehension system. Multi-stream models maintaining the N400 as integration crucially rely on the presence of a semantically attractive plausible alternative interpretation to account for the absence of an N400 effect in response to certain semantic anomalies, as reported in previous studies. The single-stream Retrieval-Integration account posits the P600 as an index of integration, further predicting that its amplitude varies continuously with integrative effort. Here, we directly test these competing hypotheses using a context manipulation design in which a semantically attractive alternative is either available or not, and target word plausibility is varied across three levels. An initial self-paced reading study revealed graded reading times for plausibility, suggesting differential integration effort. A subsequent ERP study showed no N400 differences across conditions, and that P600 amplitude is graded for plausibility. These findings are inconsistent with the interpretation of the N400 as an index of integration, as no N400 effect emerged even in the absence of a semantically attractive alternative. By contrast, the link between plausibility, reading times, and P600 amplitude supports the view that the P600 is a continuous index of integration effort. More generally, our results support a single-stream architecture and eschew the need for multi-stream 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.

On the nature of semantic constraints on lexical access.

We present two eye-tracking experiments that investigate lexical frequency and semantic context constraints in spoken-word recognition in German. In both experiments, the pivotal words were pairs of nouns overlapping at onset but varying in lexical frequency. In Experiment 1, German listeners showed an expected frequency bias towards high-frequency competitors (e.g., Blume, 'flower') when instructed to click on low-frequency targets (e.g., Bluse, 'blouse'). In Experiment 2, semantically constraining context increased the availability of appropriate low-frequency target words prior to word onset, but did not influence the availability of semantically inappropriate high-frequency competitors at the same time. Immediately after target word onset, however, the activation of high-frequency competitors was reduced in semantically constraining sentences, but still exceeded that of unrelated distractor words significantly. The results suggest that (1) semantic context acts to downgrade activation of inappropriate competitors rather than to exclude them from competition, and (2) semantic context influences spoken-word recognition, over and above anticipation of upcoming referents.

Rational Redundancy in Referring Expressions: Evidence from Event-related Potentials.

In referential communication, Grice's Maxim of Quantity is thought to imply that utterances conveying unnecessary information should incur comprehension difficulties. There is, however, considerable evidence that speakers frequently encode redundant information in their referring expressions, raising the question as to whether such overspecifications hinder listeners' processing. Evidence from previous work is inconclusive, and mostly comes from offline studies. In this article, we present two event-related potential (ERP) experiments, investigating the real-time comprehension of referring expressions that contain redundant adjectives in complex visual contexts. Our findings provide support for both Gricean and bounded-rational accounts. We argue that these seemingly incompatible results can be reconciled if common ground is taken into account. We propose a bounded-rational account of overspecification, according to which even redundant words can be beneficial to comprehension to the extent that they facilitate the reduction of listeners' uncertainty regarding the target referent.

When components collide: Spatiotemporal overlap of the N400 and P600 in language comprehension.

The problem of spatiotemporal overlap between event-related potential (ERP) components is generally acknowledged in language research. However, its implications for the interpretation of experimental results are often overlooked. In a previous experiment on the functional interpretation of the N400 and P600, it was argued that a P600 effect to implausible words was largely obscured - in one of two implausible conditions - by an overlapping N400 effect of semantic association. In the present ERP study, we show that the P600 effect of implausibility is uncovered when the critical condition is tested against a proper baseline condition which elicits a similar N400 amplitude, while it is obscured when tested against a baseline condition producing an N400 effect. Our findings reveal that component overlap can result in the apparent absence or presence of an effect in the surface signal and should therefore be carefully considered when interpreting ERP patterns. Importantly, we show that, by factoring in the effects of spatiotemporal overlap between the N400 and P600 on the surface signal, which we reveal using rERP analysis, apparent inconsistencies in previous findings are easily reconciled, enabling us to draw unambiguous conclusions about the functional interpretation of the N400 and P600 components. Overall, our results provide compelling evidence that the N400 reflects lexical retrieval processes, while the P600 indexes compositional integration of word meaning into the unfolding utterance interpretation.

Retrieval (N400) and integration (P600) in expectation-based comprehension.

Expectation-based theories of language processing, such as Surprisal theory, are supported by evidence of anticipation effects in both behavioural and neurophysiological measures. Online measures of language processing, however, are known to be influenced by factors such as lexical association that are distinct from-but often confounded with-expectancy. An open question therefore is whether a specific locus of expectancy related effects can be established in neural and behavioral processing correlates. We address this question in an event-related potential experiment and a self-paced reading experiment that independently cross expectancy and lexical association in a context manipulation design. We find that event-related potentials reveal that the N400 is sensitive to both expectancy and lexical association, while the P600 is modulated only by expectancy. Reading times, in turn, reveal effects of both association and expectancy in the first spillover region, followed by effects of expectancy alone in the second spillover region. These findings are consistent with the Retrieval-Integration account of language comprehension, according to which lexical retrieval (N400) is facilitated for words that are both expected and associated, whereas integration difficulty (P600) will be greater for unexpected words alone. Further, an exploratory analysis suggests that the P600 is not merely sensitive to expectancy violations, but rather, that there is a continuous relation. Taken together, these results suggest that the P600, like reading times, may reflect a meaning-centric notion of Surprisal in language comprehension.

Neurobehavioral Correlates of Surprisal in Language Comprehension: A Neurocomputational Model.

Expectation-based theories of language comprehension, in particular Surprisal Theory, go a long way in accounting for the behavioral correlates of word-by-word processing difficulty, such as reading times. An open question, however, is in which component(s) of the Event-Related brain Potential (ERP) signal Surprisal is reflected, and how these electrophysiological correlates relate to behavioral processing indices. Here, we address this question by instantiating an explicit neurocomputational model of incremental, word-by-word language comprehension that produces estimates of the N400 and the P600-the two most salient ERP components for language processing-as well as estimates of "comprehension-centric" Surprisal for each word in a sentence. We derive model predictions for a recent experimental design that directly investigates "world-knowledge"-induced Surprisal. By relating these predictions to both empirical electrophysiological and behavioral results, we establish a close link between Surprisal, as indexed by reading times, and the P600 component of the ERP signal. The resultant model thus offers an integrated neurobehavioral account of processing difficulty in language comprehension.

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.

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.

Visual scenes trigger immediate syntactic reanalysis: evidence from ERPs during situated spoken comprehension.

A central topic in sentence comprehension research is the kinds of information and mechanisms involved in resolving temporary ambiguity regarding the syntactic structure of a sentence. Gaze patterns in scenes during spoken sentence comprehension have provided strong evidence that visual scenes trigger rapid syntactic reanalysis. However, they have also been interpreted as reflecting nonlinguistic, visual processes. Furthermore, little is known as to whether similar processes of syntactic revision are triggered by linguistic versus scene cues. To better understand how scenes influence comprehension and its time course, we recorded event-related potentials (ERPs) during the comprehension of spoken sentences that relate to depicted events. Prior electrophysiological research has observed a P600 when structural disambiguation toward a noncanonical structure occurred during reading and in the absence of scenes. We observed an ERP component with a similar latency, polarity, and distribution when depicted events disambiguated toward a noncanonical structure. The distributional similarities further suggest that scenes are on a par with linguistic contexts in triggering syntactic revision. Our findings confirm the interpretation of previous eye movement studies and highlight the benefits of combining ERP and eye-tracking measures to ascertain the neuronal processes enabled by, and the locus of attention in, visual contexts.

Learning to attend: a connectionist model of situated language comprehension.

Evidence from numerous studies using the visual world paradigm has revealed both that spoken language can rapidly guide attention in a related visual scene and that scene information can immediately influence comprehension processes. These findings motivated the coordinated interplay account (Knoeferle & Crocker, 2006) of situated comprehension, which claims that utterance-mediated attention crucially underlies this closely coordinated interaction of language and scene processing. We present a recurrent sigma-pi neural network that models the rapid use of scene information, exploiting an utterance-mediated attentional mechanism that directly instantiates the CIA. The model is shown to achieve high levels of performance (both with and without scene contexts), while also exhibiting hallmark behaviors of situated comprehension, such as incremental processing, anticipation of appropriate role fillers, as well as the immediate use, and priority, of depicted event information through the coordinated use of utterance-mediated attention to the scene.

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.

A Neurocomputational Model of the N400 and the P600 in Language Processing.

Ten years ago, researchers using event-related brain potentials (ERPs) to study language comprehension were puzzled by what looked like a Semantic Illusion: Semantically anomalous, but structurally well-formed sentences did not affect the N400 component-traditionally taken to reflect semantic integration-but instead produced a P600 effect, which is generally linked to syntactic processing. This finding led to a considerable amount of debate, and a number of complex processing models have been proposed as an explanation. What these models have in common is that they postulate two or more separate processing streams, in order to reconcile the Semantic Illusion and other semantically induced P600 effects with the traditional interpretations of the N400 and the P600. Recently, however, these multi-stream models have been called into question, and a simpler single-stream model has been proposed. According to this alternative model, the N400 component reflects the retrieval of word meaning from semantic memory, and the P600 component indexes the integration of this meaning into the unfolding utterance interpretation. In the present paper, we provide support for this "Retrieval-Integration (RI)" account by instantiating it as a neurocomputational model. This neurocomputational model is the first to successfully simulate the N400 and P600 amplitude in language comprehension, and simulations with this model provide a proof of concept of the single-stream RI account of semantically induced patterns of N400 and P600 modulations.

The role of prosody in the interpretation of structural ambiguities: a study of anticipatory eye movements.

An eye-tracking experiment examined whether prosodic cues can affect the interpretation of grammatical functions in the absence of clear morphological information. German listeners were presented with scenes depicting three potential referents while hearing temporarily ambiguous SVO and OVS sentences. While case marking on the first noun phrase (NP) was ambiguous, clear case marking on the second NP disambiguated sentences towards SVO or OVS. Listeners interpreted case-ambiguous NP1s more often as Subject, and thus expected an Object as upcoming argument, only when sentence beginnings carried an SVO-type intonation. This was revealed by more anticipatory eye movements to suitable Patients (Objects) than Agents (Subjects) in the visual scenes. No such preference was found when sentence beginnings had an OVS-type intonation. Prosodic cues were integrated rapidly enough to affect listeners' interpretation of grammatical function before disambiguating case information was available. We conclude that in addition to manipulating attachment ambiguities, prosody can influence the interpretation of constituent order ambiguities.

The coordinated interplay of scene, utterance, and world knowledge: evidence from eye tracking.

Two studies investigated the interaction between utterance and scene processing by monitoring eye movements in agent-action-patient events, while participants listened to related utterances. The aim of Experiment 1 was to determine if and when depicted events are used for thematic role assignment and structural disambiguation of temporarily ambiguous English sentences. Shortly after the verb identified relevant depicted actions, eye movements in the event scenes revealed disambiguation. Experiment 2 investigated the relative importance of linguistic/world knowledge and scene information. When the verb identified either only the stereotypical agent of a (nondepicted) action, or the (nonstereotypical) agent of a depicted action as relevant, verb-based thematic knowledge and depicted action each rapidly influenced comprehension. In contrast, when the verb identified both of these agents as relevant, the gaze pattern suggested a preferred reliance of comprehension on depicted events over stereotypical thematic knowledge for thematic interpretation. We relate our findings to language comprehension and acquisition theories.