Sensitivity to local sentence context information in lexical ambiguity resolution: evidence from left- and right-hemisphere-damaged individuals

Using a cross-modal semantic priming paradigm, the present study investigated the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use local sentence context information to resolve lexically ambiguous words. Critical sentences were manipulated such that they were either unbiased, or biased toward one of two meanings of sentence-final equibiased ambiguous words. Sentence primes were presented auditorily, followed after a short (0 ms) or long (750 ms) interstimulus interval (ISI) by the presentation of a first- or second-meaning related visual target, on which subjects made a lexical decision. At the short ISI, neither patient group appeared to be influenced by context, in sharp contrast to the performance of the NBD control subjects. LHD nonfluent aphasic subjects activated both meanings of ambiguous words regardless of context, whereas RHD subjects activated only the first meaning in unbiased and second-meaning biased contexts. At the long ISI, LHD nonfluent aphasic subjects failed to show evidence of activation of either meaning, while RHD individuals activated first meanings in unbiased contexts and contextually appropriate meanings in second-meaning biased contexts. These findings suggest that both left (LH) and right hemisphere (RH) damage lead to deficits in using local contextual information to complete the process of ambiguity resolution. LH damage seems to spare initial access to word meanings, but initially impairs the ability to use context and results in a faster than normal decay of lexical activation. RH damage appears to initially disrupt access to context, resulting in an over-reliance on frequency in the activation of ambiguous word meanings.     

Revisiting effects of contextual strength on the subordinate bias effect: Evidence from eye movements

In this study, we examined two issues regarding the role of context in ambiguity resolution: whether access to the contextually appropriate meaning is exhaustive or selective, and whether the contextually inappropriate meaning is inhibited. Participants read texts in which a biased ambiguous word was encountered twice while their eye movements were measured. The context preceding the first encounter varied in the extent to which the subordinate meaning was supported; the context preceding the second encounter always supported the dominant meaning. The findings suggest that lexical access is exhaustive but can be influenced by context, and that the subsequent accessibility of the contextually inappropriate meaning is unaffected by previous selection processes. The results were interpreted in terms of the assumptions of the reordered-access model and activation mechanisms that operate during reading.     

Context and lexical access: implications of nonword interference for lexical ambiguity resolution

To eliminate potential "backward" priming effects, Glucksberg, Kreuz, and Rho (1986) introduced a variant of the cross-modal lexical priming task in which subjects made lexical decisions to nonword targets that were modeled on a word related to either the contextually biased or unbiased sense of an ambiguous word. Lexical decisions to nonwords were longer than controls only when the nonword was related to the contextually biased sense of the ambiguous word, leading Glucksberg et al. to conclude that context does constrain lexical access and that the multiple access pattern observed in previous studies was probably an artifact of backward priming. We did not find nonword interference when the nonword targets used by Glucksberg et al. were preceded by semantically related ambiguous or unambiguous word primes. However, we did replicate their sentence context results when the ambiguous words were removed from the sentences. We conclude that the interference obtained by Glucksberg et al. is due to postlexical judgements of the congruence of the sentence context and the target, not to context constraining lexical access.     

Accessing lexical ambiguity: Effects of context and dominance

Summary The paper examines the effects of sentential context and frequency of meaning (dominance) on the lexical access of ambiguous words. Two experiments were carried out using Swinney's (1979) cross-modal paradigm. The sentential contexts were constructed in such a way as to make salient the most characteristic features of either the dominant (Experiment 1) or the secondary (Experiment 2) meaning of the ambiguous word. The claim was that if context is sufficiently constraining selective access of the congruent meaning can be obtained. Consistent with this prediction, context biasing the dominant meaning facilitated lexical decision only on target words related to the dominant meaning. When context biased the secondary meaning, both context and dominance produced a facilitation effect.The research reported here was supported by grants from the Ministero della Pubblica Istruzione (fondi 40%) and the Consiglio Nazionale delle Ricerche     

无语境条件下汉语词类歧义词的意义激活

以单字词为实验材料,采用启动命名任务,在孤立词条件下考察了汉语词类歧义词不同意义激活的时间进程特点。实验发现,歧义词的两种意义都能被激活,但主要意义激活得较早,次要意义激活速度较慢;当两种意义都激活之后,次要意义的激活水平降低,而主要意义仍维持在一定激活水平。结果表明,汉语词类歧义词的多重激活过程会受到意义相对频率的影响。     

Sentence context effects and the timecourse of lexical ambiguity resolution in nonfluent aphasia

In the current neurolinguistic literature, two proposals have been put forth to account for the deficit in ambiguous word processing observed in nonfluent aphasic patients. One proposal maintains that these individuals are impaired in the selective access of ambiguous word meanings, while the other argues that they are impaired in the process of contextual selection. In the present study, nonfluent aphasic patients and elderly control subjects participated in a semantic priming experiment, in which ambiguous words were presented in different biasing contexts at both a 0- and 750-ms ISI. At both ISIs, control subjects showed context-selective access, in that only contextually appropriate meanings were activated. In contrast, at the 0-ms ISI, the nonfluent aphasic patients showed activation of both meanings of the ambiguous word regardless of context. Only at the 750-ms ISI did they exhibit context-selective access. These results are consistent with the proposal that left hemisphere damage causing nonfluent aphasia results in an impairment in rapidly integrating lexical-semantic information into context.     

Accessing ambiguous words during sentence comprehension

In five experiments visual processing of sentences containing either a more frequent or a less frequent usage of an ambiguous word was examined. When prior or subsequent context was pragmatically related to the relevant sense of the ambiguous word, sentences intending the more frequent sense produced longer ambiguity detection times and shorter immediate comprehension times than sentences intending the less frequent sense. This relative frequency effect was not obtained in comprehension of corresponding unambiguous sentences containing relatively high or low frequency unambiguous synonyms of the senses. These results suggest that access of ambiguous word-senses tends to occur in order of relative frequency, and that multiple access of senses tends only to occur for low frequency usages. When the preceding verb imposed selection constraints on which sense could follow, the frequency effect did not occur consistently; and it was virtually eliminated when biasing context took the form of a previous sentence containing an unambiguous synonym of the relevant sense. Implications for models of access of unambiguous words in sentences, as well as for models of processing ambiguous sentences, are considered.     

Selection mechanisms in reading lexically ambiguous words

Readers' eye movements were monitored as they read sentences containing lexically ambiguous words. The ambiguous words were either biased (one strongly dominant interpretation) or nonbiased. Readers' gaze durations were longer on nonbiased than biased words when the disambiguating information followed the target word. In Experiment 1, reading times on the disambiguating word did not differ whether the disambiguation followed the target word immediately or occurred several words later. In Experiment 2, prior disambiguation eliminated the long gaze durations on nonbiased target words but resulted in long gaze durations on biased target words if the context demanded the subordinate meaning. The results indicate that successful integration of one meaning with prior context terminates the search for alternative meanings of that word. This results in selective (single meaning) access when integration of a dominant meaning is fast (due to a biasing context) and identification of a subordinate meaning is slow (a strongly biased ambiguity with a low-frequency meaning).     

汉语双字多义词的识别优势效应

采用词汇判断法、命名法考察汉语双字多义词的识别优势效应。结果发现,在词汇判断任务中存在着多义词较单义词的识别优势,但这种识别优势只表现在低频词中。在命名任务中未发现多义词的识别优势。作者根据分布表征模型的观点对双字多义词的识别优势效应做出了可能的解释。     

Understanding words in sentence contexts: the time course of ambiguity resolution

Spoken language comprehension requires rapid integration of information from multiple linguistic sources. In the present study we addressed the temporal aspects of this integration process by focusing on the time course of the selection of the appropriate meaning of lexical ambiguities ("bank") in sentence contexts. Successful selection of the contextually appropriate meaning of the ambiguous word is dependent upon the rapid binding of the contextual information in the sentence to the appropriate meaning of the ambiguity. We used the N400 to identify the time course of this binding process. The N400 was measured to target words that followed three types of context sentences. In the concordant context, the sentence biased the meaning of the sentence-final ambiguous word so that it was related to the target. In the discordant context, the sentence context biased the meaning so that it was not related to the target. In the unrelated control condition, the sentences ended in an unambiguous noun that was unrelated to the target. Half of the concordant sentences biased the dominant meaning, and the other half biased the subordinate meaning of the sentence-final ambiguous words. The ISI between onset of the target word and offset of the sentence-final word of the context sentence was 100 ms in one version of the experiment, and 1250 ms in the second version. We found that (i) the lexically dominant meaning is always partly activated, independent of context, (ii) initially both dominant and subordinate meaning are (partly) activated, which suggests that contextual and lexical factors both contribute to sentence interpretation without context completely overriding lexical information, and (iii) strong lexical influences remain present for a relatively long period of time.     

Automatic access of the meanings of ambiguous words in context: Some limitations of knowledge-based processing

Five experiments are described on the processing of ambiguous words in sentences. Two classes of ambiguous words (noun-noun and noun-verb) and two types of context (priming and nonpriming) were investigated using a variable stimulus onset asynchrony (SOA) priming paradigm. Noun-noun ambiguities have two semantically unrelated readings that are nouns (e.g., PEN, ORGAN); noun-verb ambiguities have both noun and verb readings that are unrelated (e.g., TIRE, WATCH). Priming contexts contain a word highly semantically or associatively related to one meaning of the ambiguous word; nonpriming contexts favor one meaning of the word through other types of information (e.g., syntactic or pragmatic). In nonpriming contexts, subjects consistently access multiple meanings of words and select one reading within 200 msec. Lexical priming differentially affects the processing of subsequent noun-noun and noun-verb ambiguities, yielding selective access of meaning only in the former case. The results suggest that meaning access is an automatic process which is unaffected by knowledge-based (“top-down”) processing. Whether selective or multiple access of meaning is observed largely depends on the structure of the ambiguous word, not the nature of the context.     

Context effects in word recognition: evidence for early interactive processing

This study investigated whether a prior context influenced lexical access as indexed by participants' electrophysiological response in the N1 from 132 to 192 ms poststimulus. Ambiguous, high-frequency (HF), and low-frequency (LF) words were presented in neutral and biasing contexts. Event-related potentials (ERPs) for ambiguous words were compared with those for unambiguous HF (word form) and LF (word meaning) control words. Word frequency effects in the N1 extended previous ERP findings. A marginal effect of context for LF words provided electrophysiological support for the context-by-frequency interaction shown in reaction time paradigms. In neutral context, responses to ambiguous words were comparable to responses to HF words, and in biasing context (where context instantiated the subordinate sense), responses to ambiguous words were comparable to responses to LF words. The results establish temporal parameters for the early operation of context in lexical access. These constraints are more consistent with an interactive than a modular account.     

Hemispheric contributions to lexical ambiguity resolution in a discourse context: evidence from individuals with unilateral left and right hemisphere lesions

In the present study, a cross-modal semantic priming task was used to investigate the ability of left-hemisphere-damaged (LHD) nonfluent aphasic, right-hemisphere-damaged (RHD) and non-brain-damaged (NBD) control subjects to use a discourse context to resolve lexically ambiguous words. Subjects first heard four-sentence discourse passages ending in ambiguous words and after an inter-stimulus interval (ISI) of either 0 or 750 ms, made lexical decisions on first- or second-meaning related visual targets. NBD control subjects, at the 0 ms ISI, only activated contextually appropriate meanings, though significant effects, as a group, were only seen in second-meaning biased contexts. Surprisingly, at the 750 ms ISI, these subjects activated both appropriate and inappropriate meanings in first-meaning biased contexts. With respect to the LHD nonfluent aphasic patients, the majority activated first meanings regardless of context at the 0 ms ISI, though effects for the group were not significant. At the 750 ms ISI, these patients again activated first meanings regardless of context, with significant effects for the group only seen in first-meaning biased contexts. With regard to the RHD patients, the majority activated second meanings regardless of context at the 0 ms ISI and first meanings regardless of context at the 750 ms ISI, though, as a group, the effects were not significant. In light of our previous findings (Grindrod & Baum, 2003, submitted), the present data are interpreted as supporting the notion that damage to the left hemisphere disrupts either lexical access processes or the time course of lexical activation, whereas damage to the right hemisphere impairs the use of context and leads to activation of ambiguous word meanings based on meaning frequency.     

Context effects in lexical access: A meta-analysis

The modularity hypothesis was evaluated in this review of 25 studies that investigated context effects in early lexical processing. Selection criteria restricted the review to priming studies and to studies that presented the target word before or at the end of the prime word. Meta-analysis was used to provide summary information about the 17 studies in the review for which effect sizes could be calculated. Overall, the analysis revealed a small effect of context on lexical access. Results provide a disconfirmation of the modularity hypothesis; although multiple interpretations of a word were sometimes accessed, the contextually appropriate interpretation was consistently more strongly activated. The lack of significant heterogeneity of variance suggests that the variability observed across studies was due to sampling error; however, task, timing of target presentation, meaning frequency, type of target, and type of context were identified as potential moderator variables.     

The study of inhibitory processes in aging with the Faust et al. paradigm (1997): methodological issues

Information provided by a word activates various potential meanings. Comprehension involves the suppression of inappropriate meanings of ambiguous words in order to finetune the intended meaning of sentences. If older adults become less efficient at inhibiting contextually irrelevant information, then multiple meanings of ambiguous words would be activated regardless of contextual bias. An alternative to multiple access was that older adults activate only the most dominant meaning of ambiguous words. According to this reservation, support for an inhibition deficit would require evidence that older adults activated the multiple meanings of ambiguous words. The effects of aging on both activation and inhibition of different meanings of ambiguous words were studied using Faust et al. (1997) paradigms. Results showed that both activation and inhibition response latency differed for the dominant and subordinate target and that the dominant meaning for one subject was not the same for another one. The implication of these results is that studies of inhibition should take dominance meaning of ambiguous word for each subject into account.     

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.     

句子语境中汉语词类歧义词的意义激活

以单字词为实验材料 ,采用跨通道启动真假字判断任务 ,在句子语境中考察汉语词类歧义词不同意义激活的特点。被试为 134名北京师范大学本科学生。实验时向被试听觉呈现含有歧义词的句子 ,且句子语境分别支持歧义词的主要或次要意义 ,以不同的ISI分别呈现与歧义词两种意义有关的视觉目标词。结果发现 ,当探测目标词在最短的ISI出现时 ,与语境支持的意义有关的目标词反应时较短 ,表明语境在歧义词加工早期促进合适意义的激活 ,同时限制不合适意义的激活。实验数据支持相互作用理论     

Contextual Strength and the Subordinate Bias Effect: Comment on Martin, Vu, Kellas, and Metcalf

Martin, Vu, Kellas, and Metcalf (this issue) claim to have demonstrated that the subordinate bias effect (when preceding context instantiates the subordinate meaning of an ambiguous word that has a highly dominant meaning, reading time on that word is lengthened) can be eliminated by strong context. They argue that this provides evidence critical to discriminating between competing models of lexical ambiguity resolution: the reordered access model (in which access of meanings for an ambiguous word is exhaustive but in which the order of access is influenced by prior disambiguating context) and the context-sensitive model (in which access is selective in the presence of prior disambiguating information). We argue that there are methodological problems with their demonstration, but even if there were not, it is unclear that the subordinate bias effect is appropriate for discriminating between competing models of lexical ambiguity resolution (the reordered access model and the context-sensitive model). The effect is an empirical finding and not a fundamental tenet of the reordered access model.     

Global context effects on processing lexically ambiguous words: Evidence from eye fixations

Readers' eye movements were monitored as they read biased ambiguous target words in the context of a short paragraph. Two aspects of context were manipulated. The global context was presented in the topic sentence of the paragraph and instantiated either the dominant or the subordinate meaning of biased ambiguous target words (those with highly dominant meanings). Local contextual information either preceded or followed the target word and was always consistent with the subordinate interpretation. Consistent with prior research, we obtained a subordinate bias effect wherein readers looked longer at the ambiguous words than control words when the preceding context instantiated the subordinate meaning. More importantly, the magnitude of the subordinate bias effect was the same when global context alone, local context alone, or local and global context combined were consistent with the subordinate meaning of the ambiguous word. The results of this study indicate that global contextual information (1) has an immediate impact on lexical ambiguity resolution when no local disambiguating information is available, (2) has no additional effect when it is consistent with local information, but (3) does have a slightly delayed effect when inconsistent with local information.     

THE EFFECT OF MEANING FREQUENCY ON PROCESSING LEXICALLY AMBIGUOUS WORDS: Evidence From Eye Fixations

Abstract —Subjects read sentences containing lexically ambiguous words while their eye movements were monitored Biased ambiguous words (those that have one highly dominant sense) were used m sentences containing a prior context that instantiated their subordinate sense Control words were matched m frequency both to the dominant and to the subordinate meaning of the ambiguous word (high- and low-frequency controls) Subjects fixated longer on both the ambiguous word and the low-frequence control than on the high-frequency control When the target was ambiguous, however, the duration of posttarget fixations was longer and the likelihood of making a regression to the target was greater than when the target was an unambiguous control The results are discussed m relation to current models of lexical ambiguity resolution