Dietmar Roehm

To Predict or Not to Predict: Influences of Task and Strategy on the Processing of Semantic Relations

We report a series of event-related potential experiments designed to dissociate the functionally distinct processes involved in the comprehension of highly restricted lexical-semantic relations (antonyms). We sought to differentiate between influences of semantic relatedness (which are independent of the experimental setting) and processes related to predictability (which differ as a function of the experimental environment). To this end, we conducted three ERP studies contrasting the processing of antonym relations (black-white) with that of related (black-yellow) and unrelated (black-nice) word pairs. Whereas the lexical-semantic manipulation was kept constant across experiments, the experimental environment and the task demands varied: Experiment 1 presented the word pairs in a sentence context of the form The opposite of X is Y and used a sensicality judgment. Experiment 2 used a word pair presentation mode and a lexical decision task. Experiment 3 also examined word pairs, but with an antonymy judgment task. All three experiments revealed a graded N400 response (unrelated > related > antonyms), thus supporting the assumption that semantic associations are processed automatically. In addition, the experiments revealed that, in highly constrained task environments, the N400 gradation occurs simultaneously with a P300 effect for the antonym condition, thus leading to the superficial impression of an extremely reduced N400 for antonym pairs. Comparisons across experiments and participant groups revealed that the P300 effect is not only a function of stimulus constraints (i.e., sentence context) and experimental task, but that it is also crucially influenced by individual processing strategies used to achieve successful task performance.

The N400 as a correlate of interpretively relevant linguistic rules: Evidence from Hindi

Classical views on the electrophysiology of language assume that different event-related potential (ERP) components index distinct linguistic subdomains. Hence, left-anterior negativities are often viewed as correlates of rule-based linguistic knowledge, whereas centro-parietal negativities (N400s) are taken to reflect (non-rule-based) semantic memory or aspects of lexical-semantic predictability. The present ERP study of case marking in Hindi challenges this clear-cut dichotomy. Though determined by a grammatical rule, the choice of subject case in Hindi is also interpretively relevant as it constrains the range of possible interpretations of the subject. For incorrect subject cases, we observed an N400, which was followed by a late positivity under certain circumstances. This finding suggests that violations of rule-based knowledge may engender an N400 when the rule is interpretively relevant.

Differential effects of saliency: An event-related brain potential study

We present event-related brain potential evidence from language comprehension that the N400-modulation during noun-phrase integration is a function of the type of referential dependency that is established (identity versus inference) and the saliency (in the following understood as the sum of factors that influence the degree of accessibility of an entity in the mental model) of the information unit that serves as an anchor for the dependency. Identity relations revealed a reduced N400 compared to inferential relations, confirming previous findings. More importantly, the investigation provides novel findings concerning the effect of saliency on noun-phrase integration: identity relations did not reveal a difference in the N400 as a function of the saliency manipulation. In contrast, inferential relations showed a more pronounced N400 with less salient anchors compared to inferential relations that involved a highly salient anchor. Moreover, no difference in N400-amplitude obtained between less salient inference-based entities and new information units. These data suggest that inferential processes are blocked in the absence of a highly accessible anchor. The findings generally indicate that the language system is not only sensitive to the kind of dependency that is established, but also to the saliency of the entity that serves as anchor for the dependency. The data further demonstrate that the processing system is responsive to semantic- and discourse-level information during the interpretation of noun-phrases.

When case meets agreement: event-related potential effects for morphology-based conflict resolution in human language comprehension.

We present event-related potential evidence from language comprehension that processing conflicts arising from the same linguistic domain and appearing within the same time range do not interact when they draw upon distinct underlying neural populations. Thus, a combined violation of two morphosyntactic information types, number-agreement and case, engendered a LAN/N400-P600 pattern, while the corresponding single violations are associated with LAN-P600 and N400-P600 responses, respectively. The absence of an interaction between the two negativities indicates that neuronal resource sharing does not result from a similarity of function, but rather requires an overlap of the underlying neuronal populations.

Prominence Facilitates Ambiguity Resolution: On the Interaction Between Referentiality, Thematic Roles and Word Order in Syntactic Reanalysis

In two eye-tracking experiments, we investigated the relationship between the subject preference in the resolution of subject-object ambiguities in German embedded clauses and semantic word order constraints (i.e., prominence hierarchies relating to the specificity/referentiality of noun phrases, case assignment and thematic role assignment). Our central research question concerned the timecourse with which prominence information is used and particularly whether it modulates the subject preference. In both experiments, we replicated previous findings of reanalysis effects for object-initial structures. Our findings further suggest that noun phrase prominence does not alter initial parsing strategies (viz., the subject preference), but rather modulates the ease of later reanalysis processes. In Experiment 1, the object case assigned by the verb did not affect the ease of reanalysis. However, the syntactic reanalysis was rendered more difficult when the order of the two arguments violated the specificity/referentiality hierarchy. Experiment 2 revealed that the initial subject preference also holds for verbs favoring an object-initial base order (i.e., dative object-experiencer verbs). However, the advantage for subject-initial sentences is neutralized in relatively late processing stages when the thematic role hierarchy and the specificity hierarchy converge to promote scrambling.

Processing flexible form-to-meaning mappings: Evidence for enriched composition as opposed to indeterminacy

Sometimes, the relationship between form and meaning in language is not one-to-one. Here, we used event-related brain potentials (ERPs) to illuminate the neural correlates of such flexible syntax–semantics mappings during sentence comprehension by examining split-intransitivity. While some (“rigid”) verbs consistently select one auxiliary, other (“flexible”) verbs do not. German speakers read sentences including rigid and flexible verbs and the auxiliaries haben (HAVE) and sein (BE). In an additional condition, flexible verbs were presented with a telicity-inducing prefix that led them to select BE via the verb-prefix combination. Auxiliary selection violations engendered an N400-late positivity response for both rigid and prefixed verbs, thus suggesting that the processing system sets up an auxiliary-based expectation for particular verb classes. For unprefixed flexible verbs, average ERPs did not show differential effects of auxiliary choice. However, additional mixed-effects analyses for these verbs including by-participant and by-item acceptabilities as covariates revealed modulations of the N400 and late positivity for HAVE-trials via by-item and by-participant acceptabilities. We argue that the N400 reflects the degree of match between auxiliary choice and the lexical class of the verb, while two distinct positivity effects correlate with (1) a well-formedness categorisation and (2) the degree to which individual participants engage in enriched composition in order to render a flexible (telic) verb compatible with a particular auxiliary choice (HAVE). These results indicate that the gradient behaviour of flexible verbs is not due to indeterminacy, but rather to a higher propensity for enriched composition that results in the coercion of aspectual specification.

The costs of being certain: Brain potential evidence for linguistic preactivation in sentence processing

Prediction in sentence comprehension is often investigated by measuring the amplitude of the N400 ERP component to words that are more or less predictable from their preceding context. The N400-linked to the activation of word-associated semantic information-is reduced for words that are predictable, indicating that preactivation can lead to facilitated processing. We addressed the question whether there is measurable neural activity related to the preactivation of linguistic information before input confirms or disconfirms this prediction. We therefore measured ERPs not only to moderately to highly predictable target words, but also to preceding adverbs. Based on two separate cloze pretests, we quantified the impact of the adverb upon the predictability of the subsequent target word. Using linear mixed-effects analyses, we could show that the N400 amplitude at the target word was inversely related to target cloze value, thus replicating the finding that prediction has a facilitative effect on semantic processing. Crucially, the N400 amplitude at the pretarget adverb was modulated by adverb impact: When adverbs increased the predictability of the following word, the N400 was more negative going. We argue that this effect is related to the preactivation of linguistic information. Our findings indicate that the specification of predictions can lead to additional processes before these predictions are confirmed or disconfirmed and that activation of word-associated information through prediction is highly comparable to activation through actual input.

Semantic prediction in language comprehension: evidence from brain potentials

ABSTRACT Do people predict specific word-forms during language comprehension? In an Event-Related Potential (ERP) study participants read German sentences with predictable (The goalkeeper claims that the slick ball was easy to CATCH.) and unpredictable (The kids boasted that the young horse was easy to SADDLE.) verbs. Verbs were either consistent with the expected word-form (catch/saddle) or inconsistent and therefore led to ungrammaticality (*catches/*saddles). ERPs within the N400 time-window were modulated by predictability but not by the surface-form of the verbs, suggesting that no exact word-forms were predicted. Based on our results we will argue that predictions included semantic rather than form-information. Furthermore, ungrammatical verbs led to a strong P600, probably due to task-saliency whereas correct unpredictable verbs elicited an anterior post-N400 positivity. Because the contexts were moderately constraining, this might reflect discourse revision processes rather than inhibition of a predicted word.

The Impact of Transitional Movements and Non-Manual Markings on the Disambiguation of Locally Ambiguous Argument Structures in Austrian Sign Language (ÖGS)

Previous studies of Austrian Sign Language (ÖGS) word-order variations have demonstrated the human processing system’s tendency to interpret a sentence-initial (case-) ambiguous argument as the subject of the clause (“subject preference”). The electroencephalogram study motivating the current report revealed earlier reanalysis effects for object-subject compared to subject-object sentences, in particular, before the start of the movement of the agreement marking sign. The effects were bound to time points prior to when both arguments were referenced in space and/or the transitional hand movement prior to producing the disambiguating sign. Due to the temporal proximity of these time points, it was not clear which visual cues led to disambiguation; that is, whether non-manual markings (body/shoulder/head shift towards the subject position) or the transitional hand movement resolved ambiguity. The present gating study further supports that disambiguation in ÖGS is triggered by cues occurring before the movement of the disambiguating sign. Further, the present study also confirms the presence of the subject preference in ÖGS, showing again that signers and speakers draw on similar strategies during language processing independent of language modality. Although the ultimate role of the visual cues leading to disambiguation (i.e., non-manual markings and transitional movements) requires further investigation, the present study shows that they contribute crucial information about argument structure during online processing. This finding provides strong support for granting these cues some degree of linguistic status (at least in ÖGS).