Children's use of language context in lexical ambiguity resolution

Lexical ambiguity resolution was examined in children aged 7 to 10 years and adults. In Experiment 1, participants heard sentences supporting one (or neither) meaning of a balanced ambiguous word in a cross-modal naming paradigm. Naming latencies for context-congruent versus context-incongruent targets and judgements of the relatedness of targets to the sentence served as indices of appropriate context use. While younger children were faster to respond to related targets regardless of the sentence context, older children and adults showed priming only for context-appropriate targets. In Experiment 2, only a single-word context preceded the homophone, and in contrast to Experiment 1, all groups showed contextual sensitivity. Individual working-memory span and inhibition ability were also measured in Experiment 2, and more mature executive function abilities were associated with greater contextual sensitivity. These findings support a developmental model whereby sentential context use for lexical ambiguity resolution increases with age, cognitive processing capacity, and reading skill.     

Slowed lexical access in nonfluent aphasia: a case study.

A list priming paradigm (LPP) was used to examine the hypothesis that nonfluent aphasics are literally slowed down in automatic access to lexical information. In this paradigm, words are presented visually, and the subject's task is to make a lexical decision on each word as quickly as possible after its presentation. As soon as a lexical decision is made on one word, that word is removed and, after a predetermined interword interval, the next word is presented. In this way, a continuous "list" effect is obtained. Prior studies with both college-age and elderly subjects using the LPP have shown that, independently of age, on the LPP, priming obtains at interword delays of 500 to 800 msec, but not at either shorter or longer interword delays. In the study reported here, the LPP was used to examine delays at which priming obtained for LD, a nonfluent aphasic with a lesion primarily in the left frontal region. Examining interword delays ranging from 500 to 1800 msec, the subject showed priming only at a delay of 1500 msec, a considerably longer delay than that at which neurologically intact subjects have shown priming. Based on these results, it is argued that while automatic access is retained, that access is much slower in a nonfluent aphasic than in neurologically intact elderly subjects. These results are discussed in terms of how slowed lexical access might impact on discourse comprehension.     

Semantic satiation and lexical ambiguity resolution.

This study examines the effects of semantic satiation on lexical ambiguity resolution. On a given trial, participants were presented with a word triad. The first word (e.g., HEART) was presented on average 2.5, 12.5, or 22.5 times, and then participants received 2 new words for relatedness judgments. The first of the two new words was always a homograph (e.g., "ORGAN") and the other word was a related or unrelated pairmate (e.g., "KIDNEY"). In Experiment 1, when blocks of trials were intermixed with concordant (e.g., "HEART-ORGAN-KIDNEY"), discordant (e.g., "PIANO-ORGAN-KIDNEY"), and neutral (e.g., "CEILING-ORGAN-KIDNEY") trials, participants did not produce evidence of semantic satiation. In a second experiment in which only concordant and neutral trials were presented, however, participants did produce evidence of semantic satiation in the concordant condition. Taken together, Experiments 1 and 2 indicate that semantic satiation of the context-appropriate meaning of a homograph may impede ambiguity resolution.     

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     

Context modulates hemispheric asymmetries in the resolution of lexical ambiguity

Previous studies have reported a hemispheric asymmetry in processing dominant (e.g., paper) and subordinate (e.g., farmer) associations of ambiguous words (e.g., pen). The majority of these studies, however, applied randomly ordered presentation and collected right-hand responses only. Generating responses solely with the right hand and the randomly ordered presentation of association type might have affected natural hemispheric expertise. We explored the putative relationships between responding hand and experimental design manipulations in processing lexical ambiguity. Ambiguous target words were laterally presented following word pairs that could be associated to the dominant or subordinate meaning of the target word. We manipulated the responding hand and the experimental context by presenting the semantic associations in a random (Experiment 1) and a blocked ordered presentation (Experiment 2). The results of Experiment 2 supported the right hemisphere expertise hypothesis, whereas the results of Experiment 1 can be best explained by the direct access model where stimuli are processed by the hemisphere receiving them first, without relying on hemispheric expertise. We conclude that without manipulating the responding hand, there is a risk of misinterpreting direct access results as evidence for hemispheric expertise. Moreover, we suggest that a blocked ordered presentation might encourage participants to use the expert hemisphere for the blocked factor. A new theoretical framework is presented to explain the findings.     

Sources of sentence constraint on lexical ambiguity resolution

Results from a series of naming experiments demonstrated that major lexical categories of simple sentences can provide sources of constraint on the interpretation of ambiguous words (homonyms). Manipulation of verb (Experiment 1) or subject noun (Experiment 2) specificity produced contexts that were empirically rated as being strongly biased or ambiguous. Priming was demonstrated for target words related to both senses of a homonym following ambiguous sentences, but only contextually appropriate target words were primed following strongly biased dominant or subordinate sentences. Experiment 3 showed an increase in the magnitude of priming when multiple constraints on activation converged. Experiments 4 and 5 eliminated combinatorial intralexical priming as an alternative explanation. Instead, it was demonstrated that each constraint was influential only insofar as it contributed to the overall semantic representation of the sentence. When the multiple sources of constraint were retained but the sentence-level representation was changed (Experiment 4) or eliminated (Experiment 5), the results of Experiments 1, 2, and 3 and were not replicated. Experiment 6 examined the issue of homonym exposure duration by using an 80-msec stimulus onset asynchrony. The results replicated the previous experiments. The overall evidence indicates that a sentence context can be made strongly and immediately constraining by the inclusion of specific fillers for salient lexical categories. The results are discussed within a constraint-based, context-sensitive model of lexical ambiguity resolution.     

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.     

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.     

Hemispheric sensitivities to lexical and contextual information: evidence from lexical ambiguity resolution

The present study examined the manner in which both hemispheres utilize prior semantic context and relative meaning frequency during the processing of homographs. Participants read sentences biased toward the dominant or the subordinate meaning of their final homograph, or unbiased neutral sentences, and performed a lexical decision task on lateralized targets presented 250ms after the onset of the sentence-final ambiguous prime. Targets were either related to the dominant or the subordinate meaning of the preceding homograph, or unrelated to it. Performance asymmetry was found in the absence of a biasing context: dominant-related targets were exclusively facilitated in the RVF/LH, whereas both dominant- and subordinate-related targets were facilitated in the LVF/RH. Performance symmetry was found in the presence of a biasing context: dominant-related targets were exclusively activated in dominant-biasing contexts, whereas both dominant- and subordinate-related targets were facilitated in subordinate-biasing contexts. The implications of the results for both general and hemispheric models of word processing are discussed.     

Eye movements and lexical ambiguity resolution: investigating the subordinate-bias effect

Recent debates on lexical ambiguity resolution have centered on the subordinate-bias effect, in which reading time is longer on a biased ambiguous word in a subordinate-biasing context than on a control word. The nature of the control word--namely, whether it matched the frequency of the ambiguous word's overall word form or its contextually instantiated word meaning (a higher or lower frequency word, respectively)--was examined. In addition, contexts that were singularly supportive of the ambiguous word's subordinate meaning were used. Eye movements were recorded as participants read contextually biasing passages that contained an ambiguous word target or a word-form or word-meaning control. A comparison of fixation times on the 2 control words revealed a significant effect of word frequency. Fixation times on the ambiguous word generally fell between those on the 2 controls and were significantly different than both. Results are discussed in relation to the reordered access model, in which both meaning frequency and prior context affect access procedures.     

The influence of global discourse on lexical ambiguity resolution

The influence of global discourse on the resolution of lexical ambiguity was examined in a series of naming experiments. Two-sentence passages were constructed to bias either the dominant or the subordinate meaning of a homonym that was embedded in a locally ambiguous sentence. The results provided evidence for the immediate (0-msec interstimulus interval) resolution of lexical ambiguity and were subsequently replicated in Experiment 2, in which an 80-msec stimulus onset asynchrony exposure duration was employed for the homonyms. Strong dominant and subordinate biased discourse contexts activated only the contextually appropriate sense of a homonym. In Experiment 3, each sentence of the discourse was presented in isolation. The pattern of activation obtained in Experiments 1 and 2 was found to be contingent on the integration of the two sentences to construct an overall global discourse representation of the text. The results support a context-sensitive model of lexical ambiguity resolution.     

Lexical ambiguity and the timecourse of attentional allocation in word recognition

In two experiments the allocation of attention during the recognition of ambiguous and unambiguous words was investigated. In Experiment 1, separate groups performed either lexical decision, auditory probe detection, or their combination. In the combined condition probes occurred 90, 180, or 270 ms following the onset of the lexical-decision target. Lexical decisions and probe responses were fastest for ambiguous words, followed by unambiguous words and pseudowords, respectively, which indicated that processing ambiguous words was less attention demanding than unambiguous words or pseudowords. Attention demands decreased across the timecourse of word recognition for all stimulus types. In Experiment 2, one group performed the lexical-decision task alone, whereas another group performed the lexical-decision task during the retention interval of a short-term memory task. The results were consistent with those from Experiment 1 and showed that word recognition is an attention-demanding process and that the demands are inversely related to the number of meanings of the stimulus. These results are discussed with regard to the structure of the mental lexicon (i.e., single vs. multiple lexical entries) and the effect of such a structure on attentional mechanisms.     

LIFG-based attentional control and the resolution of lexical ambiguities in sentence context

The role of attentional control in lexical ambiguity resolution was examined in two patients with damage to the left inferior frontal gyrus (LIFG) and one control patient with non-LIFG damage. Experiment 1 confirmed that the LIFG patients had attentional control deficits compared to normal controls while the non-LIFG patient was relatively unimpaired. Experiment 2 showed that all three patients did as well as normal controls in using biasing sentence context to resolve lexical ambiguities involving balanced ambiguous words, but only the LIFG patients took an abnormally long time on lexical ambiguities that resolved toward a subordinate meaning of biased ambiguous words. Taken together, the results suggest that attentional control plays an important role in the resolution of certain lexical ambiguities - those that induce strong interference from context-inappropriate meanings (i.e., dominant meanings of biased ambiguous words).     

Phonological ambiguity and lexical ambiguity: effects on visual and auditory word recognition

Three experiments in Serbo-Croatian were conducted on the effects of phonological ambiguity and lexical ambiguity on printed word recognition. Subjects decided rapidly if a printed and a spoken word matched or not. Printed words were either phonologically ambiguous (two possible pronunciations) or unambiguous. If phonologically ambiguous, either both pronunciations were real words or only one was, the other being a nonword. Spoken words were necessarily unambiguous. Half the spoken words were auditorily degraded. In addition, the relative onsets of speech and print were varied. Speed of matching print to speech was slowed by phonological ambiguity, and the effect was amplified when the stimulus was also lexically ambiguous. Auditory degradation did not interact with print ambiguity, suggesting that perception of the spoken word was independent of the printed word.     

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.     

Eye movements and spoken language comprehension: effects of visual context on syntactic ambiguity resolution

When participants follow spoken instructions to pick up and move objects in a visual workspace, their eye movements to the objects are closely time-locked to referential expressions in the instructions. Two experiments used this methodology to investigate the processing of the temporary ambiguities that arise because spoken language unfolds over time. Experiment 1 examined the processing of sentences with a temporarily ambiguous prepositional phrase (e.g., "Put the apple on the towel in the box") using visual contexts that supported either the normally preferred initial interpretation (the apple should be put on the towel) or the less-preferred interpretation (the apple is already on the towel and should be put in the box). Eye movement patterns clearly established that the initial interpretation of the ambiguous phrase was the one consistent with the context. Experiment 2 replicated these results using prerecorded digitized speech to eliminate any possibility of prosodic differences across conditions or experimenter demand. Overall, the findings are consistent with a broad theoretical framework in which real-time language comprehension immediately takes into account a rich array of relevant nonlinguistic context.     

Enhancement of naming in nonfluent aphasia through gesture

In a number of studies that have examined the gestural disturbance in aphasia and the utility of gestural interventions in aphasia therapy, a variable degree of facilitation of verbalization during gestural activity has been reported. The present study examined the effect of different unilateral gestural movements on simultaneous oral-verbal expression, specifically naming to confrontation. It was hypothesized that activation of the phylogenetically older proximal motor system of the hemiplegic right arm in the execution of a communicative but nonrepresentational pointing gesture would have a facilitatory effect on naming ability. Twenty-four aphasic patients, representing five aphasic subtypes, including Broca's, Transcortical Motor, Anomic, Global, and Wernicke's aphasics were assessed under three gesture/naming conditions. The findings indicated that gestures produced through activation of the proximal (shoulder) musculature of the right paralytic limb differentially facilitated naming performance in the nonfluent subgroup, but not in the Wernicke's aphasics. These findings may be explained on the view that functional activation of the archaic proximal motor system of the hemiplegic limb, in the execution of a communicative gesture, permits access to preliminary stages in the formative process of the anterior action microgeny, which ultimately emerges in vocal articulation.     

Structural influences on the resolution of lexical ambiguity: an analysis of hemispheric asymmetries

Structural influences on lexical ambiguity resolution in the two cerebral hemispheres was investigated using a divided visual field procedure. Participants were presented with auditory Wh- sentences containing an ambiguous word, where the grammatical role of the word was apparent only at a sentence-final verb (e.g., "Which BANK did the woman see?"). Following a sentence, either immediately or after 600 ms, a target word was presented in either the right or left visual field. Targets were related to the ambiguous word's dominant meaning (MONEY), the subordinate meaning (RIVER), or were unrelated. With left visual field presentation, priming occurred for both dominant- and subordinate-related targets at a 0 ms delay, but only for dominant-related targets at 600 ms. With left visual field presentation, priming occurred for subordinate-related targets only at both delays. The results suggest that grammatical assignment triggers the selection of meaning in the left hemisphere, whereas processing in the right hemisphere operates independently of structural analyses.     

维吾尔族与汉族的大学生在汉语歧义词消解中的语境促进效应及反应抑制效应

词汇歧义是语言的普遍现象。在汉语中, 歧义词的种类繁多, 是少数民族学生汉语学习困难的重要原因之一。通过两个实验, 考察在不同加工时间条件下维吾尔族和汉族的大学生在汉语歧义词消解中的语境促进效应及抑制效应。结果发现, 两个民族的大学生均出现了语境促进效应, 但在短时加工条件下, 汉族大学生的语境促进效应显著大于维吾尔族大学生, 在长时加工条件下, 两个民族的大学生的语境促进效应并无显著差异。在短时加工条件下, 仅汉族大学生可以有效地抑制无关信息的干扰; 在长时加工条件下, 两个民族的大学生均可以有效地抑制无关信息的干扰。整个研究表明, 在汉语歧义词消解中, 随着加工时间增加, 维吾尔族大学生的语境促进效应和对无关信息的抑制均可以达到与汉族大学生相近的水平。     

Grammatical category ambiguity in aphasia

This study asked whether aphasic adults show different noun/verb retrieval patterns based upon their clinical categorization as fluent or nonfluent. Participants selected either the noun or the verb meaning of target words, as presented in three contexts. The framework was that nouns (associated with temporal lobe function) are processed, stored, and retrieved separately from verbs (associated with frontal lobe function), implying separate status in the mental lexicon. Stimuli were homophonic homographs, words that are spelled and pronounced the same but which have different meanings (in this case, noun and verb meanings). Another contrast was the putative difference between systematic pairs (e.g., "kiss" and "farm"), in which noun and verb meanings are transparently related, and may be stored as a unit, and unsystematic pairs (e.g., "squash" and "sink"), in which noun and verb meanings are apparently unrelated, implying discrete storage. Results demonstrated significant interactions between fluent and nonfluent participants, suggesting that, as expected, fluent aphasic adults have more difficulty with nouns, nonfluent aphasic adults have more difficulty with verbs. There was no effect of systematicity. Contrary to expectations, verbs proved less vulnerable, rather than more vulnerable, to aphasic impairment.