The role of animacy and thematic relationships in processing active English sentences: evidence from event-related potentials

Recent event-related potential studies report a P600 effect to incongruous verbs preceded by semantically associated inanimate noun-phrase (NP) arguments, e.g., "eat" in "At breakfast the eggs would eat...". This P600 effect may reflect the processing cost incurred when semantic-thematic relationships between critical verbs and their preceding NP argument(s) bias towards different interpretations to those dictated by their sentences' syntactic structures. We have termed such violations of alternative thematic roles, 'thematic role violations.' Semantic-thematic relationships are influenced both by semantic associations and by more basic semantic features, such as a noun's animacy. This study determined whether a P600 effect can be evoked by verbs whose thematic structures are violated by their preceding inanimate NP arguments, even in the absence of close semantic-associative relationships with these arguments or their preceding contexts. ERPs were measured to verbs under four conditions: (1) non-violated ("At breakfast the boys would eat..."); (2) preceded by introductory clauses and animate NPs that violated their pragmatic expectations but not their thematic structures ("At breakfast the boys would plant..."); (3) preceded by semantically related contexts but inanimate NPs that violated their thematic structures ("At breakfast the eggs would eat..."); (4) preceded by semantically unrelated contexts and inanimate NPs that also violated their thematic structures ("At breakfast the eggs would plant..."). Pragmatically non-thematic role violated verbs preceded by unrelated contexts and animate NPs evoked robust N400 effects and small P600 effects. Thematically violated verbs preceded by inanimate argument NPs evoked robust P600 effects but no N400 effects, regardless of whether these inanimate arguments or their preceding contexts were semantically related or unrelated to these verbs. These findings suggest that semantic-thematic relations, related to animacy constraints on verbs' arguments, are computed online and can immediately impact verb processing within active, English sentences.     

Is the P600/SPS affected by the richness of semantic content? A linguistic ERP study in Swedish

The study investigated whether the P600/SPS component is sensitive to the richness of semantic content in sentences. ERPs were recorded while 30 native Swedish speakers read sentences, of which half were syntactically correct and half contained a syntactic violation. Both kinds of sentences came in one of three types of descending semantic completeness: semantically coherent sentences, sentences which were incoherent due to violations of selectional restrictions, or sentences of pseudo words, hence void of lexical content. In the semantically coherent sentences a P600/SPS was found for the syntactic violation. A less salient positivity was found for the violation in the semantically incoherent sentences. No P600/SPS was found for the syntactic violation in the pseudo word sentences and no LAN component in any sentence type. The results are interpreted as supporting the hypothesis that the P600/SPS component reflects a semantically based reanalysis process.     

Learning to divide the labor: an account of deficits in light and heavy verb production

Theories of sentence production that involve a convergence of activation from conceptual‐semantic and syntactic‐sequential units inspired a connectionist model that was trained to produce simple sentences. The model used a learning algorithm that resulted in a sharing of responsibility (or “division of labor”) between syntactic and semantic inputs for lexical activation according to their predictive power. Semantically rich, or “heavy”, verbs in the model came to rely on semantic cues more than on syntactic cues, whereas semantically impoverished, or “light”, verbs relied more on syntactic cues. When the syntactic and semantic inputs were lesioned, the model exhibited patterns of production characteristic of agrammatic and anomic aphasic patients, respectively. Anomic models tended to lose the ability to retrieve heavy verbs, whereas agrammatic models were more impaired in retrieving light verbs. These results obtained in both sentence production and single‐word naming simulations. Moreover, simulated agrammatic lexical retrieval was more impaired overall in sentences than in single‐word tasks, in agreement with the literature. The results provide a demonstration of the division‐of‐labor principle, as well as general support for the claim that connectionist learning principles can contribute to the understanding of non‐transparent neuropsychological dissociations.     

EEG theta and gamma responses to semantic violations in online sentence processing

We explore the nature of the oscillatory dynamics in the EEG of subjects reading sentences that contain a semantic violation. More specifically, we examine whether increases in theta ( approximately 3-7 Hz) and gamma (around 40 Hz) band power occur in response to sentences that were either semantically correct or contained a semantically incongruent word (semantic violation). ERP results indicated a classical N400 effect. A wavelet-based time-frequency analysis revealed a theta band power increase during an interval of 300-800 ms after critical word onset, at temporal electrodes bilaterally for both sentence conditions, and over midfrontal areas for the semantic violations only. In the gamma frequency band, a predominantly frontal power increase was observed during the processing of correct sentences. This effect was absent following semantic violations. These results provide a characterization of the oscillatory brain dynamics, and notably of both theta and gamma oscillations, that occur during language comprehension.     

An event-related fMRI study of syntactic and semantic violations

We used event-related functional magnetic resonance imaging to identify brain regions involved in syntactic and semantic processing. Healthy adult males read well-formed sentences randomly intermixed with sentences which either contained violations of syntactic structure or were semantically implausible. Reading anomalous sentences, as compared to well-formed sentences, yielded distinct patterns of activation for the two violation types. Syntactic violations elicited significantly greater activation than semantic violations primarily in superior frontal cortex. Semantically incongruent sentences elicited greater activation than syntactic violations in the left hippocampal and parahippocampal gyri, the angular gyri bilaterally, the right middle temporal gyrus, and the left inferior frontal sulcus. These results demonstrate that syntactic and semantic processing result in nonidentical patterns of activation, including greater frontal engagement during syntactic processing and larger increases in temporal and temporo-parietal regions during semantic analyses.     

On the Brain Response to Syntactic Anomalies: Manipulations of Word Position and Word Class Reveal Individual Differences

In two experiments, event-related brain potentials (ERPs) were recorded from 13 scalp locations while subjects read sentences containing a syntactically or a semantically anomalous word. The position (sentence-embedded vs sentence-final) and word class (open vs closed) of the syntactic anomalies were manipulated. In both experiments, semantically anomalous words elicited an enhanced N400 component. Syntactically anomalous closed class words elicited a widely distributed late positive wave (P600) regardless of the word's position and a smaller negative-going effect that was largest over anterior sites when the anomaly occurred in sentence-final position. The response to syntactically anomalous open class words revealed striking qualitative individual differences: These words elicited a P600 response in the majority of subjects and an N400 response in others. The proportion of subjects exhibiting the N400 response was greater when the anomaly occurred in sentence-final position. These results are interpreted in the context of prior findings, and implications for the hypothesis that syntactic and semantic anomalies elicit distinct brain potentials are discussed.     

Lexical integration: Sequential effects of syntactic and semantic information

Both semantic and syntactic context constraints can influence word processing at the level of lexical integration. In event-related brain potentials (ERPs), semantic integration is reflected by a negativity around 400 msec (N400), whereas phrase structure assignment and syntactic integration are assumed to be reflected by an early left anterior negativity and a late positivity (P600), respectively. An ERP study is presented in which participants read different types of sentences whose terminal verb was either congruent with the preceding context or incongruent due to a phrase structure violation, a semantic violation, or both. The main finding was that only the pure semantic violation condition, but not the combined semantic and syntactic violation condition, elicited a large N400. The two conditions containing phrase structure violations were predominantly characterized by a P600. Both semantic violation conditions, moreover, displayed a late negativity around 700 msec that overlapped with the P600 in the double violation condition. The absence of an N400 effect for elements that are syntactically as well as semantically incongruent with prior context suggests an early influence of phrase structure information on processes of lexical-semantic integration. The present data are discussed in comparison to previous ERP findings, and a new view of lexical integration processes is proposed.     

Effects of syntactic category assignment on lexical ambiguity resolution in reading: an eye movement analysis

Readers' eye movements were monitored as they read sentences containing lexically ambiguous words whose meanings share a single syntactic category (e.g., calf), lexically ambiguous words whose meanings belong to different syntactic categories (e.g., duck), or unambiguous control words. Information provided prior to the target always unambiguously specified the context-appropriate syntactic-category assignment for the target. Fixation times were longer on ambiguous words whose meanings share a single syntactic category than on controls, both when prior context was semantically consistent with the subordinate interpretation of a biased ambiguous word (Experiment 1) and when prior context was semantically neutral as to the intended interpretation of a balanced ambiguous word (Experiment 2). These ambiguity effects, which resulted from differences in difficulty with meaning resolution, were not found when the ambiguity crossed syntactic categories. These data indicate that, in the absence of syntactic ambiguity, syntactic-category information mediates the semantic-resolution process.     

Friendly drug-dealers and terrifying puppies: Affective primacy can attenuate the N400 effect in emotional discourse contexts

Words that are semantically congruous with their preceding discourse context are easier to process than words that are semantically incongruous with their context. This facilitation of semantic processing is reflected by an attenuation of the N400 event-related potential (ERP). We asked whether this was true of emotional words in emotional contexts where discourse congruity was conferred through emotional valence. ERPs were measured as 24 participants read two-sentence scenarios with critical words that varied by emotion (pleasant, unpleasant, or neutral) and congruity (congruous or incongruous). Semantic predictability, constraint, and plausibility were comparable across the neutral and emotional scenarios. As expected, the N400 was smaller to neutral words that were semantically congruous (vs. incongruous) with their neutral discourse context. No such N400 congruity effect was observed on emotional words following emotional discourse contexts. Rather, the amplitude of the N400 was small to all emotional words (pleasant and unpleasant), regardless of whether their emotional valence was congruous with the valence of their emotional discourse context. However, consistent with previous studies, the emotional words produced a larger late positivity than did the neutral words. These data suggest that comprehenders bypassed deep semantic processing of valence-incongruous emotional words within the N400 time window, moving rapidly on to evaluate the words’ motivational significance.     

A discourse on semantic priming

The processing of a word is sometimes affected if earlier words are semantically related to it (semantic “priming”). Priming phenomena have generally been interpreted as reflecting the organization of the mental lexicon. Past studies have shown that priming effects have a very fast rise time and a relatively rapid decay time. This paper investigates the rate of decay of semantic facilitation in both sentences and lists. It was hypothesized that sentence processing involves the construction of a discourse model in which the main topics stay active. If true, then words referring to related objects or events will be processed rapidly even if they occur later in the input, i.e., there will be no decay of facilitation. Three experiments with college students examined the relative time to process a critical word when it was preceded by either a pair of semantically related words or more neutral words. The materials occurred in either sentences or lists, the latter being word-level anagrams of the sentences. Subjects carried out the phonememonitoring task, responding to a word-initial target phoneme that occurred immediately after the critical word. In Experiments I (N = 58) and II (N = 40) 12 words separated the related/neutral words and the critical items. Facilitation in processing the critical word was present in sentences but not in lists. Experiment III (N = 128) showed that the amount of facilitation in sentences was the same when 12 words separated the related/neutral and critical words as when 1.5 words separated them. Thus, there was no evidence obtained here for decay of facilitation in sentences. The results are taken to be consistent with a discourse-model interpretation of semantic facilitation in sentences.     

The dynamic influence of emotional words on sentence comprehension: An ERP study

In the present study, we explored the influence of emotional words on the semantic integration of their following neutral nouns during sentence comprehension. We manipulated the emotionality of verbs and the semantic congruity of their following (neutral) object nouns in sentences. Event-related potentials were recorded to the verbs, which were either negative or neutral, and to the object nouns, which were either semantically congruent or incongruent relative to the preceding contexts. We found an N400 and a P600 effect in response to the semantic congruity of the nouns when they followed the neutral verbs. However, the P600 (but not the N400) semantic congruity effect may have been attenuated when the nouns followed the negative verbs. Meanwhile, the negative verbs elicited a larger P2 and N400 than did the neutral verbs. The results indicate that the attention captured by emotional words impaired reanalysis of the following incongruent information, demonstrating a dynamic influence of emotional words on the semantic processing of following information during sentence comprehension.     

The comprehension of anomalous sentences: evidence from structural priming

We report three experiments investigating how people process anomalous sentences, in particular those in which the anomaly is associated with the verb. We contrast two accounts for the processing of such anomalous sentences: a syntactic account, in which the representations constructed for anomalous sentences are similar in nature to the ones constructed for well-formed sentences; and a semantic account, in which the representations constructed for anomalous sentences are erroneous, or altogether missing, and interpretation is achieved on the basis of semantic representations instead. To distinguish between these accounts, we used structural priming. First, we ruled out the possibility that anomaly per se influences the magnitude of the priming effect: Prime sentences with morphologically incorrect verbs produced similarly enhanced priming (lexical boost) to sentences with the same correct verbs (Exp. 1). Second, we found that prime sentences with a novel verb (Exp. 2) or a semantically and syntactically incongruent verb (Exp. 3) produced a priming effect, which was the same as that produced by well-formed sentences. In accord with the syntactic account, we conclude that the syntactic representations of anomalous sentences are similar to those constructed for well-formed sentences. Our results furthermore suggest that lexically-independent syntactic information is robust enough to produce well-formed syntactic representations during processing without requiring aid from lexically-based syntactic information.     

Memory effects in syntactic ERP tasks

The study presented here investigated the role of memory in normal sentence processing by looking at ERP effects to normal sentences and sentences containing grammatical violations. Sentences where the critical word was in the middle of the sentence were compared to sentences where the critical word always occurred in sentence-final position. Grammaticality judgments were required at the end of the sentence. While the violations in both conditions result in the expected increase in the P600 component (reflecting the fact that the syntactic violation is being processed), the sentences with the sentence-medial critical word also result in a late frontal negativity effect. It is hypothesized that this effect is due to greater memory requirements that are needed to keep the violation in mind until a response can be made at the end of the sentence. The maintenance of the decision that a sentence is ungrammatical must be kept in memory longer for sentence-medial violations as opposed to when the violation occurs at the end of the sentence (immediately preceding the moment at which the judgment can be made).     

The effects of slowed speech on auditory comprehension in aphasia

The present study investigates the effects of slowed speech on auditory comprehension in aphasia. Specifically, an attempt was made to isolate the effects of added time on comprehension at the language processing stages of auditory perception, by increasing the duration of the vowel segments in each word; word recognition and semantic analysis, by adding silences between words; and syntactic analysis, by adding silences at constituent phrase boundaries. Sentences were also read at a slow rate to see the effects of naturally slowed speech on sentence comprehension. Test sentences consisted of simple active and passive declarative sentences, and complex sentences with embedded medial and final relative clauses. Sentences were either semantically reversible or nonreversible. Thirty-four aphasic patients who varied in both severity and type of aphasia were tested on a picture verification task. Results indicated that slowing facilitated language comprehension significantly only in the syntactic condition. Neither syntactic complexity nor semantic reversibility interacted with slowed speech to facilitate auditory language comprehension. Further, it was only the Wernicke's aphasics who showed significant improvement with time added at constituent boundaries. These results suggest that time alone does not facilitate language comprehension in aphasia, but that rather it is the interaction of time with syntactic processing which improves comprehension.     

Rapid extraction of gist from visual text and its influence on word recognition

Two experiments explored rapid extraction of gist from a visual text and its influence on word recognition. In both, a short text (sentence) containing a target word was presented for 200 ms and was followed by a target recognition task. Results showed that participants recognized contextually anomalous word targets less frequently than contextually consistent counterparts (Experiment 1). This context effect was obtained when sentences contained the same semantic content but with disrupted syntactic structure (Experiment 2). Results demonstrate that words in a briefly presented visual sentence are processed in parallel and that rapid extraction of sentence gist relies on a primitive representation of sentence context (termed protocontext) that is semantically activated by the simultaneous presentation of multiple words (i.e., a sentence) before syntactic processing.     

The generalizability of context effects on word recognition: A reconsideration of the roles of parafoveal priming and sentence context

In three experiments, subjects named target words preceded by congruous, incongruous, or neutral sentence contexts. There was no evidence that the recognition of the target word was affected by the semantic characteristics of a word presented immediately to the right of it. The nature of the preceding sentence context did affect target-naming speed. However, the magnitude of the context effect was considerably smaller in these experiments, in which nonterminal target words were used, than in previous experiments in which the target word was always the final word of the sentence, was highly predictable from the context, and was often semantically related to words in the sentence. The implications of these two findings for theories of reading and context effects are discussed.     

Influences of semantic and syntactic context on open- and closed-class words

Event-related potentials (ERPs) were recorded as subjects read semantically meaningful, syntactically legal but nonsensical and random word strings. The constraints imposed by formal sentence structure alone did not reduce the amplitude of the N400 component elicited by open-class words, whereas semantic constraints did. Semantic constraints also eliminated the word-frequency effect of a larger N400 for low-frequency words. Responses to closed-class words exhibited reduced N400 amplitudes in syntactic and congruent sentences, indicating that formal sentence structure placed greater restrictions on closed-class words than it did on open-class words. However, unlike the open-class results, the impact of sentence context on closed-class words was stable across word positions, suggesting that these syntactic constraints were applied only locally. A second ERP component, distinct from the N400, was elicited primarily by congruent closed-class words.     

The role of syntactic context in word recognition

This study examines the role of syntactic information in word recognition. Subjects made a word-nonword decision regarding a target string that was preceded by a syntactically appropriate word, a semantically related word, or an unrelated word. In Experiment 1, with syntactic and semantic trials assigned to separate blocks, syntactically and semantically appropriate context significantly reduced lexical decision for subsequent target words, compared with unrelated contexts. In Experiment 2, the syntactically and semantically primed trials were either blocked separately or mixed within the same block. Significant syntactic and semantic effects were both observed in the blocked condition, but only the semantic effect was obtained in the mixed condition     

Repetition in the transcortical aphasias

Transcortical aphasic patients were assessed on a repetition task comprised of both well-formed and deviant sentences. The patients faithfully repeated those sentences that were factually incorrect but grammatically well formed, and those sentences that were ungrammatical because of selection restriction violations. In contrast, presented with sentences featuring only minor syntactic violations (e.g., lack of number agreement), the patients spontaneously, and without awareness, resisted exact repetition; moreover, the resultant changes most often served to correct the syntactic deviations. Repetitions of sentences of this latter type also revealed a difference between the patients as a function of level of comprehension. The transcortical motor aphasic patient was influenced by semantic factors in his alterations of the minor syntactic violations, while the transcortical sensory aphasic was not. These findings are discussed in relation to the notion of autonomous syntactic processing. They are taken to suggest that syntactic facts such as number agreement are represented at a level in the processing chain that is distinct from that of semantic representation.     

The Understanding of Word Definitions in School-Age Children

This study investigated children’s understanding of unfamiliar noun and verb definitions in tasks that were manipulated for syntactic and semantic properties of definitions. The study was also designed to examine the relation between understanding word definitions and the skills of syntactic awareness and making inferences. A total of 117 children over three upper elementary grades (3, 4, 5) participated in the study. The definitional tasks were presented in multiple choice format, with each definition followed by four context sentences. In the syntactic/semantic condition, which included nouns and verbs, the context sentences were manipulated for syntactic and semantic properties. In the semantic condition, which included only nouns, the context sentences were manipulated only for semantics. All children also completed a syntactic awareness task and a making inferences task. Results indicated that children did not make significant grade improvements in the semantic task, but did so in the syntactic/semantic task, suggesting the dependence of syntactic cues on definitional understanding. Findings further suggested that inferencing and syntactic awareness are important to children’s ability in understanding a definition for an unfamiliar word and to integrating that meaning into a context sentence.