Ambiguity in the brain: what brain imaging reveals about the processing of syntactically ambiguous sentences

Two fMRI studies investigated the time course and amplitude of brain activity in language-related areas during the processing of syntactically ambiguous sentences. In Experiment 1, higher levels of activation were found during the reading of unpreferred syntactic structures as well as more complex structures. In Experiments 2A and 2B higher levels of brain activation were found for ambiguous sentences compared with unambiguous sentences matched for syntactic complexity, even when the ambiguities were resolved in favor of the preferred syntactic construction (despite the absence of this difference in previous reading time results). Although results can be reconciled with either serial or parallel models of sentence parsing, they arguably fit better into the parallel framework. Serial models can admittedly be made consistent but only by including a parallel component. The fMRI data indicate the involvement of a parallel component in syntactic parsing that might be either a selection mechanism or a construction of multiple parses.     

Temporal course of activation of the antecedent by the reflexive in syntactically ambiguous sentences in Japanese

Three experiments examined the temporal course of the activation of an antecedent triggered by a reflexive,jibun, in syntactically ambiguous sentences in Japanese. Twenty-two students in Experiment 1 were tested for sentences where a subject word occupied the first position and an indirect object word the second, with the probe given for each word either immediately after the reflexive or at the end of the sentence. Reaction times (RTs) were faster when the probe was for subject (S-probe) than when it was for indirect object (IO-probe) irrespective of the probe position. Experiment 2 tested 22 students to determine the effect of order of mention of participant on the probe recognition time. RTs were faster for the S-probe than for the IO-probe, although the difference between the two probes was smaller when the probe was given immediately after the reflexive. Experiment 3 tested 22 students to examine the effect of context on an activation pattern. RTs were lower for the S-probe than for the IO-probe, though no difference was found between them for the probe given at the end of the sentence. Findings were interpreted as supporting the single-interpretation model for on-line analysis of syntactically ambiguous sentences and also the immediate-activation model in an assignment of the reflexive to its antecedent.     

Processing doubly quantified sentences: Evidence from eye movements

We investigated the processing of doubly quantified sentences, such asKelly showed a photo to every critic, that are ambiguous as to whether the indefinite (a photo) specifies single or multiple referents. Ambiguity resolution requires the computation of relative quantifier scope: Whether a or every takes wide scope, thereby determining how many entities or events are to be represented. In an eye-tracking experiment, we manipulated quantifier order and whether continuations were singular or plural, for constructions with the direct or the indirect object occurring first. We obtained effects consistent with the on-line processing of relative scope at the doubly quantified phrase and considered two possible explanations for a preference for singular continuations to the quantified sentence. We conclude that relative quantifier scope is computed on line during reading but may not be a prerequisite for the resolution of definite anaphors, unless required by secondary tasks.     

Processing phonological and semantic ambiguity: evidence from semantic priming at different SOAs.

Disambiguation of heterophonic and homophonic homographs was investigated in Hebrew using semantic priming. Ambiguous primes were followed by unambiguous targets at 100 ms, 250 ms, and 750 ms stimulus onset asynchrony (SOA). Lexical decision for targets related to the dominant phonological alternatives of heterophonic homographs were facilitated at all SOAs. Targets related to subordinate alternatives were facilitated only at SOAs of 250 ms or longer. When the primes were homophonic homographs, semantic relationship facilitated lexical decision of targets at all SOAs regardless of the dominance of the meaning to which the targets were related. These data can be accounted for by assuming multiple lexical entries for heterophonic homographs, single lexical entries for homophonic homographs, and phonological mediation of accessing meanings. Language-specific factors probably account for the long-lasting activation of subordinate meanings.     

To end ambiguous sentences

A study of the time required to complete ambiguous sentences suggested that: even though Ss are unaware of the ambiguity while completing sentences, they take more time to complete ambiguous sentences than unambiguous ones: the degree of difficulty in completing ambiguous sentences is related to the linguistic level at which the ambiguity occurs: sentences containing two ambiguities are more difficult to complete than those containing only one, and when these two ambiguities occur at different linguistic levels, these sentences are harder to complete than when both occur within the same linguistic level: ambiguity may affect the grammaticality and relevance of completions; and may cause stuttering and laughter, even without awareness of the ambiguity. An attempt to fit these results to several theories of the processing of ambiguous sentences led us to the conclusion that ambiguity interferes with our understanding of a single meaning of a sentence, and that the degree of interference varies with the linguistic level at which the ambiguity occurs.     

Plausibility and subcategorization preference in children's processing of temporarily ambiguous sentences: Evidence from self-paced reading

Three self-paced reading experiments investigated children's processing of temporarily ambiguous sentences. Across the three experiments, subcategorization preference of a verb in a subordinate clause and the semantic plausibility of the misanalysis were manipulated. Reading times in the temporarily ambiguous region and following syntactic disambiguation indicated that children in the age range tested (8 years, 11 months to 12 years, 11 months) routinely misanalyse sentences of the type tested, and their tendency to misanalyse the sentences does not depend on the subcategorization preferences of the initial verb. Additional correlational analyses suggested that subcategory information did affect the degree of difficulty that readers experienced processing the critical noun and matrix verb.     

To end ambiguous sentences

A study of the time required to complete ambiguous sentences suggested that: even though Ss are unaware of the ambiguity while completing sentences, they take more time to complete ambiguous sentences than unambiguous ones: the degree of difficulty in completing ambiguous sentences is related to the linguistic level at which the ambiguity occurs: sentences containing two ambiguities are more difficult to complete than those containing only one, and when these two ambiguities occur at different linguistic levels, these sentences are harder to complete than when both occur within the same linguistic level: ambiguity may affect the grammaticality and relevance of completions; and may cause stuttering and laughter, even without awareness of the ambiguity. An attempt to fit these results to several theories of the processing of ambiguous sentences led us to the conclusion that ambiguity interferes with our understanding of a single meaning of a sentence, and that the degree of interference varies with the linguistic level at which the ambiguity occurs.     

Phonological and semantic priming: Evidence for task-independent effects

The questions asked in the present experiments concern the generality of semantic and phonological priming effects: Do these effects arise automatically regardless of target task, or are these effects restricted to target tasks that specifically require the retrieval of the primed information? In Experiment 1, subjects produced faster color matching times on targets preceded by a masked rhyming prime than on targets preceded by an orthographic control or an unrelated prime. This result suggests that automatic priming effects on the basis of phonological similarity can be obtained even when the target task does not make use of phonological information. This claim was reinforced in Experiment 2 in which a rhyme priming effect and a semantic priming effect were found in a semantic categorization task. In Experiment 3, the target task was phonological (rhyme detection), and, again, both phonological and semantic priming effects were observed. Finally, in Experiments 4 and 5, in a replication and an extension of Experiment 1, phonological and semantic priming effects were found in a color matching task, a task involving neither phonological nor semantic processing. These results are most straightforwardly interpreted by assuming that both semantic and phonological priming effects are, at least in part, due to automatic activation of memorial representations.     

Spatial distance effects on incremental semantic interpretation of abstract sentences: Evidence from eye tracking

A large body of evidence has shown that visual context information can rapidly modulate language comprehension for concrete sentences and when it is mediated by a referential or a lexical-semantic link. What has not yet been examined is whether visual context can also modulate comprehension of abstract sentences incrementally when it is neither referenced by, nor lexically associated with, the sentence. Three eye-tracking reading experiments examined the effects of spatial distance between words (Experiment 1) and objects (Experiment 2 and 3) on participants’ reading times for sentences that convey similarity or difference between two abstract nouns (e.g., ‘Peace and war are certainly different...’). Before reading the sentence, participants inspected a visual context with two playing cards that moved either far apart or close together. In Experiment 1, the cards turned and showed the first two nouns of the sentence (e.g., ‘peace’, ‘war’). In Experiments 2 and 3, they turned but remained blank. Participants’ reading times at the adjective (Experiment 1: first-pass reading time; Experiment 2: total times) and at the second noun phrase (Experiment 3: first-pass times) were faster for sentences that expressed similarity when the preceding words/objects were close together (vs. far apart) and for sentences that expressed dissimilarity when the preceding words/objects were far apart (vs. close together). Thus, spatial distance between words or entirely unrelated objects can rapidly and incrementally modulate the semantic interpretation of abstract sentences.     

Effects of syntactic information on semantic access of ambiguous verbs in spoken language comprehension: Evidence from a cross‐modal priming experiment1

Abstract: The aim of this study was to examine how syntactic information affects the semantic processing of ambiguous verbs in spoken Japanese. The effect of a postpositional particle on semantic access of an ambiguous verb at the end of the sentence was demonstrated in two kinds of sentences, S‐ga‐V sentences (subject, subjective postpositional particle, and ambiguous verb) and O‐wo‐V sentences (object, objective postpositional particle, and ambiguous verb). A cross‐modal priming method was used in which a target noun was presented visually in Kanji (Chinese) characters either one syllable before the end or immediately after the end of the ambiguous verb. Weak multiple priming occurred in the one‐syllable‐before condition, followed by selective access in the immediately after condition, but this multiple access was partially constrained by the preceding postpositional particle. A brief occurrence of multiple access and rapid transition to selective access were detected. Furthermore, objective particles were found to have stronger constraints on multiple access than on subjective particles. A connectionist model using a constraint‐based lexical approach was consistent with the experimental results.     

Verb semantic structures in memory for sentences: Evidence for componential representation

This research contrasts two hypotheses concerning componential storage of meaning. The Complexity Hypothesis assumed by Fodor (The language of thought, NY: Crowell, 1975), Kintsch (The representation of meaning in memory, Hillsdale, NJ: Erlbaum, 1974), and Thorndyke (Conceptual complexity and imagery in comprehension and memory. Journal of Verbal Learning and Verbal Behavior, 1975, 14, 359–369) states that a word with many semantic components will require more processing resources, comprehension time, and long-term memory space than a word with few components, and thus will interfere more with memory for surrounding words. This memory prediction was tested against an alternative prediction based on connectivity. The Connectivity Hypothesis views verb semantic structures as frames for sentence representation and states that memory strength between two nouns in a sentence increases with the number of underlying verb subpredicates that connect the nouns. Thus, the Complexity Hypothesis predicts that a verb with many subpredicates will lead to poorer memory strength between the surrounding nouns than a verb with few subpredicates, while the Connectivity Hypothesis predicts that verbs with many subpredicates will lead to greater memory strength between nouns in cases when the additional subpredicates provide semantic connections between the nouns.In three experiments, subjects recalled subject-verb-object sentences, given subject nouns as cues. General verbs, with relatively few subpredicates, were compared with more specific verbs whose additional subpredicates either did or did not provide additional connections between the surrounding nouns. The level of recall of the object noun, given the subject noun as cue, was predicted by the relative number of connecting subpredicates in the verb, but not by the relative number of subpredicates. This finding supports the Connectivity Hypothesis over the Complexity Hypothesis. These results are interpreted in terms of a model in which the verb conveys a structured set of subpredicates that provides a connective framework for sentence memory.     

Latent semantic analysis cosines as a cognitive similarity measure: Evidence from priming studies

In distributional semantics models (DSMs) such as latent semantic analysis (LSA), words are represented as vectors in a high-dimensional vector space. This allows for computing word similarities as the cosine of the angle between two such vectors. In two experiments, we investigated whether LSA cosine similarities predict priming effects, in that higher cosine similarities are associated with shorter reaction times (RTs). Critically, we applied a pseudo-random procedure in generating the item material to ensure that we directly manipulated LSA cosines as an independent variable. We employed two lexical priming experiments with lexical decision tasks (LDTs). In Experiment 1 we presented participants with 200 different prime words, each paired with one unique target. We found a significant effect of cosine similarities on RTs. The same was true for Experiment 2, where we reversed the prime-target order (primes of Experiment 1 were targets in Experiment 2, and vice versa). The results of these experiments confirm that LSA cosine similarities can predict priming effects, supporting the view that they are psychologically relevant. The present study thereby provides evidence for qualifying LSA cosine similarities not only as a linguistic measure, but also as a cognitive similarity measure. However, it is also shown that other DSMs can outperform LSA as a predictor of priming effects.     

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.     

Novel word integration in the mental lexicon: Evidence from unmasked and masked semantic priming

We sought to establish whether novel words can become integrated into existing semantic networks by teaching participants new meaningful words and then using these new words as primes in two semantic priming experiments, in which participants carried out a lexical decision task to familiar words. Importantly, at no point in training did the novel words co-occur with the familiar words that served as targets in the primed lexical decision task, allowing us to evaluate semantic priming in the absence of direct association. We found that familiar words were primed by the newly related novel words, both when the novel word prime was unmasked (Experiment 1) and when it was masked (Experiment 2), suggesting that the new words had been integrated into semantic memory. Furthermore, this integration was strongest after a 1-week delay and was independent of explicit recall of the novel word meanings: Forgetting of meanings did not attenuate priming. We argue that even after brief training, newly learned words become an integrated part of the adult mental lexicon rather than being episodically represented separately from the lexicon.     

Processing ambiguous verbs: evidence from eye movements

In 2 eye-tracking experiments, participants read verbs that had 2 (unrelated) meanings or 2 (related) senses in contexts that disambiguated before or after the verb, to the dominant or subordinate interpretation. A 3rd experiment used unambiguous verbs. The results indicated that the language processor used information about context in the early stages of resolving meaning ambiguities but only during integration for sense ambiguities. Effects of preference were delayed for both types of verbs. The results contrast with findings concerning the processing of nouns (e.g., K. Rayner & S. A. Duffy, 1986). For meaning ambiguities, the authors argue that delays in resolution allow both meanings to reach a high level of activation, thus reducing effects of frequency. For sense ambiguities, the authors argue that the processor does not access multiple senses but activates one underspecified meaning and uses context to home in on the appropriate sense.     

Dissociative effects of viewpoint and semantic priming on action and semantic decisions: Evidence for dual routes to action from vision

This article reports evidence that two variables—object viewpoint and semantic priming—differentially affect action and semantic decisions to objects. Changing the viewing angle of an object, so that its graspable parts are oriented away from observers, disrupted action decisions but had little effect on semantic categorization. In contrast, semantic priming influenced semantic categorization and object naming, but not action decisions. Action priming, however, did not affect performance. These selective effects are consistent with the existence of separate semantic and direct (nonsemantic) routes to action from vision.     

The comprehension and verification of ambiguous sentences

When Ss are presented with an ambiguous sentence they tend to interpret it in only one way. If later events warrant, Ss can recover the other meaning, a process which takes time. These conclusions follow from the results of a study in which 40 undergraduate Ss verified whether or not pictures shown at the end of a sentence represented the meaning of the sentence. When ambiguous sentences were presented, the verification time (VT) was no slower than for unambiguous sentences if the picture represented the “expected” meaning (as determined on a pre-test) of the ambiguity. The VT to the picture representing the “unexpected” meaning of the ambiguity was longer than VT to corresponding control sentences.     

Processing novel compounds: Evidence for interactive meaning activation of ambiguous nouns

In three experiments, the meaning activation of ambiguous nouns in novel nominal compounds was investigated. Ambiguous nouns were unbalanced homographs occurring as the second members of the compound. Meaningful interpretations of the compounds were based on either the dominant or the subordinate meaning of the ambiguous noun. In Experiment 1, visually presented novel compounds serving as primes were followed at varying intervals by targets associatively related to distinct meanings of the ambiguous noun. In a lexical decision task, facilitation effects were found only for targets related to the meaning that was relevant for the interpretation of the compound. Experiment 2 showed that interactive activation could not be attributed to differences in semantic relatedness between the first members of compounds and targets. Experiment 3 demonstrated equal intralexical relatedness between members for both types of compounds. It is proposed that interactive activation may facilitate the interpretation of the novel compound. Compatible meaning aspects of the nouns may become more strongly activated, and incompatible meaning aspects may not become activated. The selection of meaning aspects relevant for interpretation would thereby be simplified.     

The structure of semantic person memory: evidence from semantic priming in person recognition

This paper reviews research on the structure of semantic person memory as examined with semantic priming. In this experimental paradigm, a familiarity decision on a target face or written name is usually faster when it is preceded by a related as compared to an unrelated prime. This effect has been shown to be relatively short lived and susceptible to interfering items. Moreover, semantic priming can cross stimulus domains, such that a written name can prime a target face and vice versa. However, it remains controversial whether representations of people are stored in associative networks based on co-occurrence, or in more abstract semantic categories. In line with prominent cognitive models of face recognition, which explain semantic priming by shared semantic information between prime and target, recent research demonstrated that priming could be obtained from purely categorically related, non-associated prime/target pairs. Although strategic processes, such as expectancy and retrospective matching likely contribute, there is also evidence for a non-strategic contribution to priming, presumably related to spreading activation. Finally, a semantic priming effect has been demonstrated in the N400 event-related potential (ERP) component, which may reflect facilitated access to semantic information. It is concluded that categorical relatedness is one organizing principle of semantic person memory.     

Parallel parsing: Evidence from reactivation in garden-path sentences

An all-visual, on-line, lexical priming technique was used to investigate whether the human sentence processor computes syntactic representations serially or in parallel. Structurally ambiguous garden-path sentences such as the following were studied: “The psychologist told the wife that the man bumpedthat her car was stolen.” Despite the strong preference for the sentential-complement reading of the ambiguous region (italicized), a reactivation effect for the head of the relative clause (wife) was observed immediately following the presentation of the embedded verb (bumped), suggesting that the relative clause analysis is also computed. This finding is taken as evidence for parallel parsing since both possible analyses were shown to have a processing reflection simultaneously: Computation of the sentential-complement analysis was demonstrated by the fact that readers garden-path when that analysis turns out to be incorrect, and computation of the relative clause analysis was demonstrated by the reactivation effect.