George Kellas

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.

Influence of contextual features on the activation of ambiguous word meanings.

Three studies examined whether initial meaning activation is sensitive to context. Experiment 1 demonstrated that contextually appropriate targets were activated more than inappropriate targets. Experiment 2 evaluated activation across intervals of 0, 300, and 600 ms. Constraining sentences activated contextually appropriate meanings over inappropriate meanings. This was maintained across the intervals for highly salient targets. Less-salient targets, although initially activated, were no longer activated 300 ms following the homograph. Experiment 3 converged on context-sensitive activation following a 50-ms exposure of the sentence-final homograph. Conclusions are (a) initial meaning activation can be sensitive to context, (b) when a homograph is instantiated, it is congruent with a broad scope of targets, and (c) less-salient targets receive less activation over the time course.

Semantic activation of noun concepts in context

A modified Stoop procedure was used to examine the role that context plays in guiding semantic access of unambiguous nouns in sentence contexts. The sentences either emphasized a high- or a low-dominant property of a noun that was the last word in the sentence or were control sentences. Each sentence was followed by the relevant high- or low-dominant property either immediately or after a 300-or 600-ms delay. There was significant color-naming interference (relative to control) for high-dominant properties regardless of biasing context in the immediate and delayed conditions. There was also significant color-naming interference for low-dominant properties in the immediate condition regardless of context. However, in the delayed conditions, the low-dominant properties led to color-naming interference only when preceded by sentence contexts biasing interpretation toward the low-dominant property. It was concluded that high-dominant properties function as core, or invariant, aspects of meaning and that initial semantic access is context independent.

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.

Strength of Discourse Context as a Determinant of the Subordinate Bias Effect

Two experiments examined the influence of strength of discourse bias on lexical ambiguity resolution. Short passages were constructed to bias polarized ambiguous words (homonyms) strongly or weakly toward the dominant or subordinate meanings. Using a self-paced reading task in Experiment 1, it was demonstrated that in strongly biased discourse, reading times for homonyms in dominant discourse did not differ from those in subordinate discourse. However, when the discourse was weakly biased, homonyms were read faster in dominant discourse than in subordinate discourse. Experiment 2 combined the reading paradigm with a naming task in order to provide an assessment of specific word-meaning activation. Reading times on ambiguous words replicated the results of Experiment 1. In addition, naming latencies for probe words revealed that only the contextually appropriate sense of a homonym was activated in strongly biased discourse. In contrast, both contextually appropriate and inappropriate senses were activated following a weakly biased subordinate discourse, whereas only the dominant sense was activated following weakly biased dominant discourse. The results demonstrate (1) an immediate influence of prior discourse information on lexical processing; and (2) that the strength of discourse constraints can play a governing role in lexical ambiguity resolution. The results were interpreted within the framework of a context-sensitive model of lexical ambiguity resolution.

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.

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.

Developmental changes in the internal structure of semantic categories

Abstract The present experiment was designed to examine the development of the cognitive representation of semantic categories. Response latencies on a classification task were compared for second, fourth, and sixth graders (8, 10, and 12 years of age, respectively) and college students. On each trial the subjects were presented with two pictures that represented either typical or atypical category exemplars. The two pictures were physically identical, nonidentical pictures from the same category, or pictures from different categories. One half of the trials were primed by presenting a category name in advance of the stimuli. In addition, stimulus degradation was manipulated in order to assess the locus of priming effects. A significant interaction of age × priming × typicality was found for physically identical stimuli. This interaction indicated that the nature of the internal representation of categories changed from the second graders to the adults. It was suggested that the second graders might weigh features inappropriately in generating semantic prototypes. The fact that stimulus degradation and priming did not interact at any age level for any of the match types indicates that priming affected a conceptual encoding stage rather than a perceptual encoding stage.

Scope of Word Meaning Activation During Sentence Processing by Young and Older Adults

In a naming experiment, we examined word meaning activation on-line during sentence processing by younger and older adults. Sentences were biased to either the most or least frequently used meaning of a sentence-final ambiguous word. In order to determine the scope of initial meaning activation, targets represented either high- or low-salient semantic relationships to a single sense of the ambiguous word in context. Both age groups evidenced context-dependent activation of word meaning. In addition, context activated a wide scope of meaning that included both high- and low-salience aspects of the ambiguous words. These results contradict predictions based on the inhibition deficit hypothesis (Hasher & Zacks, 1988). However, they are compatible with an interactive activation model of language comprehension that does not discriminate among age groups.

Development aspects of storage and retrieval

Abstract The present investigation examined the developmental characteristics of memory. For this purpose, the performance of third, fifth, and seventh graders was dichotomized into storage and retrieval phases. The storage phase was evaluated by analyses of overt rehearsal which yielded data on the amount and distribution of rehearsal during list presentation. Subject-paced free and serial recall tasks were used to provide control conditions to assess the extent to which externalized rehearsal changed the characteristics of overt processing. Correct responding and order of recall provided data relevant to the retrieval phase. Comparisons among the various measures indicated that (1) the amount of rehearsal increased with age, (2) the number of different items which are rehearsed at a given time increased with age, (3) both the amount and distribution of rehearsal were related to the level of correct responding, and (4) the order of item retrieval became increasingly serial with age. In addition, it was demonstrated that a marked change occurred in the nature of storage processing between the fifth and seventh grades.