Greg B. Simpson

Cerebral Hemispheric Mechanisms in the Retrieval of Ambiguous Word Meanings

Targets related to ambiguous primes were projected to the left and right visual fields in a lexical priming experiment with stimulus onset asynchronies (SOA) of 35 and 750 msec. Right visual field results were similar to our earlier results with central projection (G. B. Simpson & C. Burgess, 1985, Journal of Experimental Psychology: Human Perception and Performance, 11, 28-39). Facilitation was found for the more frequent meaning at both SOAs and a decrease in facilitation for the less frequent meaning at the longer SOA. In contrast, left visual field results indicated a decay of facilitation for the more frequent meaning at the longer SOA, while activation for the subordinate meaning increased. Results suggest that, while automatic processing occurs in both hemispheres, only the left hemisphere engages in controlled processing of ambiguous word meanings. In addition, the present results support the idea that the right hemisphere has a special role in ambiguity resolution and that the right hemisphere lexicon possesses a richer endowment than earlier thought.

Meaning Dominance and Semantic Context in the Processing of Lexical Ambiguity.

Two experiments investigated the processing of ambiguous words. In the first, lexical decisions were made to words related to the dominant or the subordinate meanings of homograph primes. Only responses for dominant associates were facilitated relative to unrelated words. In the second experiment, ambiguous words ended sentences that varied in the degree to which they biased the dominant or the subordinate meaning of the homograph. Following ambiguous sentences, dominant meanings were retrieved first. When the sentence was strongly biased toward either meaning, only that meaning was retrieved. Only when the sentence was weakly biased toward the subordinate meaning was more than one meaning retrieved. Dominance and context apparently make independent contributions to the processing of ambiguous words.

Selective access of homograph meanings in sentence context

Abstract Two experiments assessed the timecourse of meaning activation for ambiguous words. Subjects read sentences ending in homographs, and named a subsequent target. When the sentence was not biased toward either meaning of the homograph, the results showed the effects of the frequency of the meanings: The dominant meaning was activated more quickly and maintained longer than the subordinate. When the sentence was strongly biased toward one meaning, only the target related to that meaning was facilitated, regardless of the interval between the sentence and the target. In the second experiment, the homographs were replaced by words to which the targets were not associated. No priming of targets was found, indicating that the results of Experiment 1 were not due to direct activation of target information by the context. The results are discussed in light of criticisms of earlier research that did not consider the timecourse of activation and in light of recent hypotheses about the nature of context effects.

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.

Lexical and Sentence Context Effects in Word Recognition

Three experiments examined lexical and sentence-level contributions to contextual facilitation effects in word recognition. Subjects named target words preceded by normal or scrambled sentence contexts that contained lexical associates of the target. In Experiment 1, normal sentences showed facilitation for related targets and inhibition for unrelated targets. Experiment 2 eliminated syntactically anomalous targets among unrelated items and showed only facilitation for related targets. In neither experiment was there any effect of relatedness for scrambled stimuli. Experiment 3 included syntactically normal but semantically anomalous sentences to test whether the failure of scrambled sentences to show priming was due to their syntactic incoherence. Normal sentences again showed contextual facilitation, but neither scrambled nor anomalous sentences showed such effects. The results indicate that there are sentence-context effects that do not arise solely from intralexical spreading activation and suggest that context facilitates the identification of a lexical candidate.

Encoding and contextual components of word recognition in good and poor readers

Good and poor readers from the third and sixth grades (9- and 12-year-olds, respectively), named visually presented words as rapidly as possible. Words were in clear or degraded form, and were preceded by related or unrelated words. Poor readers were hurt more by degradation than were good readers, and showed greater benefit from context. In general, the contextual benefit was greater with degraded words than with intact, and this interaction was especially pronounced in the poor readers. The results are consistent with an interactive-compensatory model of word recognition. Under conditions in which stimulus encoding is slow, contextual factors may compensate for this encoding deficit.

Effect of backward priming on word recognition in single-word and sentence contexts.

Backward priming was investigated under conditions similar to those used in lexical ambiguity research. Subjects received prime-target word pairs that were associated either unidirectionally (BABY-STORK) or bidirectionally (BABY-CRY). In the first experiment, targets were presented 500 ms following the onset of visual primes, and subjects made naming or lexical decision responses to the targets. Forward priming was obtained in all conditions, while backward priming (i.e., priming for pairs in which there was a unidirectional target-to-prime association, as in BABY-STORK) occurred only with lexical decision. In the second experiment, primes were presented auditorily, either in isolation or in a sentence. Targets followed the offset of the primes either immediately or after 200 ms. Backward priming occurred with both response tasks, but only when the prime was an isolated word. In addition, backward priming decreased over time with the naming task, but not with lexical decision. These results suggest that the locus of the backward priming effect is different for the two response tasks. Further, the lack of a backward priming effect with sentence contexts suggests that backward priming cannot account for the demonstrations of multiple access in the lexical ambiguity literature. These results, therefore, support a context-independent view of lexical access.

Chapter 3 Contextual Feature Activation and Meaning Access

Publisher Summary This chapter (1) proposes the context critical in determining what aspects of word meaning becomes activated during reading comprehension; (2) critically evaluates a task currently accepted as least problematic for the study of meaning access, followed by a discussion of an alternate methodology; and (3) describes research that makes use of normatively derived stimuli that represent the features activated by specific sentences. The chapter also discusses that current efforts to specify the locus of context effects on meaning retrieval by prematurely considering the greater issue of what is activated by context in general.

Dual-task performance as a function of adult age and task complexity.

A dual-task procedure was used to examine capacity demands of letter-matching in younger and older adults. Older subjects generally were slower on both tasks than were younger adults, but this difference was especially pronounced for the late stages of category matching, suggesting that retrieval and comparison of category information is particularly demanding for older adults.

Implications of Lexical Ambiguity Resolution for Word Recognition and Comprehension

Publisher Summary The implications of the lexical ambiguity problem go far beyond words with multiple dictionary entries. The issues involved in lexical ambiguity research are applicable to a wide range of comprehension phenomena. The selection processes that typify ambiguous words are, to some extent, relevant to all lexical access because all words normally have more information associated with them than is required in any particular context. Word-level ambiguity only exemplifies in an obvious way, because of characteristics that exist at virtually all levels of language comprehension. It is suggested in the chapter that phenomena such as metaphor, idiom, and indirect requests present a comprehender with essentially the same interpretive dilemma occasioned by words with more than one possible meaning. The chapter reviews briefly some of the recent research in lexical ambiguity and additionally discusses extensions of lexical ambiguity research to other issues of word recognition. It also describes a series of studies using lexical ambiguity to explore qualitative changes that occur with development of the ability to use context in facilitating word recognition, a problem to which the methodology of ambiguity seems very well suited.