Hemispheric differences in context sensitivity during lexical ambiguity resolution

Three experiments were conducted to investigate the influence of contextual constraint on lexical ambiguity resolution in the cerebral hemispheres. A cross-modal priming variant of the divided visual field task was utilized in which subjects heard sentences containing homonyms and made lexical decisions to targets semantically related to dominant and subordinate meanings. Experiment 1 showed priming in both hemispheres of dominant meanings for homonyms embedded in neutral sentence contexts. Experiment 2 showed priming in both hemispheres of dominant and subordinate meanings for homonyms embedded in sentence contexts that biased a central semantic feature of the subordinate meaning. Experiment 3 showed priming of dominant meanings in the left hemisphere (LH), and priming of the subordinate meaning in the right hemisphere (RH) for homonyms embedded in sentences that biased a peripheral semantic feature of the subordinate meaning. These results are consistent with a context-sensitive model of language processing that incorporates differential sensitivity to semantic relationships in the cerebral hemispheres.     

Bihemispheric processing of redundant bilateral lexical information

Cerebral asymmetries in lexical ambiguity resolution were studied. In 2 experiments, targets related to the dominant and subordinate meanings of ambiguous word primes were presented for lexical decision after a 750-ms stimulus onset asynchrony. Experiment 1 compared presentation of target words to the left visual field/right-hemisphere (LVF/RH), to the right visual field/left-hemisphere (RVF/LH), or after redundant bilateral visual field (BVF) presentation. Experiment 2 examined unilateral priming in the absence of a BVF condition. On unilateral trials, priming was observed for dominant meanings in both the LVF/RH and RVF/LH, whereas subordinate priming was obtained only in the RVF/LH. These results suggest a possible role of hemispheric interaction in the availability of ambiguous word meanings. BVF performance evidenced a bilateral redundancy gain and priming that resembled that obtained on RVF/LH trials. Additional BVF analyses were not consistent with a strict race model interpretation and appear to implicate hemispheric cooperation in the bihemisperic processing of lexical information.     

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 msec, 250 msec, and 750 msec stimulus onset asynchrony (SOA). Lexical decision for targets related to the dominant phonological alternatives of heterophonic homographs was facilitated at all SOAs. Targets related to subordinate alternatives were facilitated only at SOAs of 250 msec or longer. When the primes were homophonic homographs, semantic relationship facilitated lexical decision to 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual insensitivity in schizophrenic language processing: Evidence from lexical ambiguity.

The authors investigated whether contextual failures in schizophrenia are due to deficits in the detection of context or the inhibition of contextually irrelevant information. Eighteen schizophrenia patients and 24 nonpsychiatric controls were tested via a cross-modal semantic priming task. Participants heard sentences containing homonyms and made lexical decisions about visual targets related to the homonyms' dominant or subordinate meanings. When sentences moderately biased subordinate meanings (e.g., the animal enclosure meaning of pen), schizophrenia patients showed priming of dominant targets (e.g., paper) and subordinate targets (e.g., pig). In contrast, controls showed priming only of subordininate targets. When contexts strongly biased subordinate meanings, both groups showed priming only of subordinate targets. The results suggest that inhibitory deficits rather than context detection deficits underlie contextual failures in schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorical priming in the cerebral hemispheres: automatic in the left hemisphere, postlexical in the right hemisphere?

Automatic and postlexical semantic processing in the cerebral hemispheres was studied by presenting categorically related but nonassociated word pairs (e.g., TABLE-BED) to the left visual field (LVF) or to the right visual field (RVF) in semantic priming experiments. Experiment 1 examined automatic priming across stimulus onset asynchronies (SOAs) of 165 and 750 ms with a low proportion of related pairs and a low nonword ratio, employing a GO-NOGO lexical decision task. In contrast to an earlier view that a larger range of meanings is automatically activated in the right than in the left hemisphere, priming was observed in the RVF/left hemisphere only. SOA did not exert any effects. In Experiment 2, postlexical semantic matching of the prime and the target was encouraged by requiring subjects to respond to both of them at the same time. Now there was priming in the LVF, suggesting that a postlexical matching process works in the right hemisphere. The earlier studies showing a right hemisphere advantage in categorical priming are reinterpreted according to the postlexical right hemisphere hypothesis.     

Crystal structure of human serum albumin complexed with fatty acid reveals an asymmetric distribution of binding sites

A lexical decision experiment investigated hemisphere asymmetries in resolving lexical ambiguity within a sentence context. Sentences that biased a single meaning (either dominant or subordinate) of sentence-final ambiguous words were followed by a lateralized target related to the sentence-congruent or -incongruent meaning of the ambiguous word, or an unrelated word. In the RVF sentence-congruent targets were facilitated, while incongruent targets were not primed. In contrast, related targets were facilitated in the LVF, regardless of sentence context. This suggests that selecting the contextually appropriate word meaning requires the left hemisphere, and supports a right hemisphere role in maintaining alternate word senses.     

The effect of time course and context on the facilitation of semantic features in the cerebral hemispheres.

Two divided visual field priming experiments were designed to determine the nature of lexical retrieval in the cerebral hemispheres by studying the facilitation of semantic features of unambiguous nouns. Unambiguous nouns have a single meaning, yet semantic features associated with these nouns may vary in the degree to which they are compatible with this single meaning (e.g., LAMB–WOOL as compared with LAMB–CHOPS). Results suggest that the left hemisphere selects both strongly and weakly associated semantic features that are compatible with the dominant representation of the noun. Dominance compatibility, rather than association strength, seems to be the more important factor for deciding what features are maintained in the left hemisphere. In contrast, the right hemisphere maintains more varied information, including features that are less compatible with the dominant representation (Experiment 1) and context information (Experiment 2). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric communication is via direct connections

Two priming experiments, using normal university students as subjects, independently projected low imagery primes and concrete target words to the left or right visual fields (LVF or RVF) to examine the merits of three spreading activation models of interhemispheric communication: (i) callosal relay of a semantically encoded prime; (ii) transfer of products activated as a result of the spread of activation; and (iii) direct connections between the hemispheres. The first experiment temporally separated pairs by a stimulus onset asynchrony (SOA) of 250 ms and obtained strong support for the direct connections model. Priming effects were obtained only when the prime was projected to the RVF and the target to the LVF. The pattern of priming effects suggested that low imagery words projected to the left hemisphere can activate concrete associates in the right hemisphere via direct callosal connections between the two. In the second experiment, the SOA was increased to 450 ms. This time, RVF-RVF priming was obtained along with RVF-LVF priming. The findings are interpreted within a modification of Bleasdale's (1987) framework, where abstract/low imagery words and concrete/high imagery words are represented in separate subsystems in the left hemisphere lexicon. Support was also found for the view that the left hemisphere is comprised of a complex network of abstract and concrete words, while the right hemisphere operates as a subsidiary word processor, subserving linguistic processing with a limited, special purpose lexicon comprised of associative connections between concrete, imageable words (e.g., Zaidel, 1983a; Bradshaw, 1980). Interhemispheric communication in the priming procedure appears to occur at the semantic level, via direct connections between the hemispheres.     

Inhibitory semantic priming of lexical decisions due to failure to retrieve weakly activated codes.

Semantic priming effects from newly learned vocabulary words are examined in a lexical decision task. At low levels of learning, those primes whose meanings are recognizable but not recallable can inhibit responses to well-known, semantically related target words, whereas those whose meaning are recallable produce either no effect or facilitation, depending on instructions concerning how to use the prime information. These results are consistent with the notion that semantic priming effects are determined at least in part by the nature of the retrieval operations performed on the prime and target, over and above influences due to spreading activation and confirmed or violated expectations. Specifically, they indicate a need to include mechanisms other than violated expectations that can produce inhibition of retrieval. Candidate mechanisms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation of working memory influences on lexical ambiguity resolution.

The present study employed a combined semantic judgment and lexical decision priming paradigm to examine the impact of working memory on the inhibitory processes of lexical ambiguity resolution. The results indicated that overall, participants activated one meaning of a presented homograph while not priming the alternative meaning. As hypothesized, participants with high working-memory spans exhibited a pattern of priming for congruent conditions and a lack of positive priming for incongruent conditions. In contrast, participants with low working-memory capacity showed priming for both congruent and incongruent conditions, but only for conditions in which the context was related to the dominant meaning of the homograph. The results suggest that people with low working-memory capacity have difficulty inhibiting inappropriate homograph meanings and further demonstrate that these difficulties may vary as a function of context-meaning dominance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric dissociations in controlled lexical–semantic processing.

Cognitive mechanisms of semantic priming in individuals with intact cerebral hemispheres were studied using the visual half-field method and lexical-decision tasks. In Experiment 1, unidirectionally associated word pairs were presented in a forward direction (e.g., BEAVER–TAIL) to isolate priming attributable to automatic activation or expectancy-based processing. Forward priming was restricted to the right visual field-left hemisphere, and it occurred only when expectancy-based processing was encouraged in the instructions. Experiments 2 and 3 found backward priming (e.g., TAIL–BEAVER) only in the left visual field, indicating that the right hemisphere contributes to retrospective semantic matching of the target back to the prime. The results suggest that the 2 hemispheres have different roles in controlled processing of semantic relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of word association and meaning frequency in a cross-modal lexical decision task: Is the priming due to "semantic" activation?

Two experiments examined the effects of priming by ambiguous, auditorily presented word primes. In related conditions, primes were followed by either associatively related or semantically related but associatively unrelated targets. When the targets were presented at prime offset (Exp 1), priming effects were observed only for associatively related targets, independent of meaning frequency (i.e., whether the target was related to the dominant or subordinate meaning of the ambiguous prime). When the targets were presented after a 700 msec delay (Exp 2), however, priming effects were observed only for targets related to the prime's dominant meaning, regardless of the nature of the prime-target relation. These results raise the strong possibility that previously reported differences in the nature of priming effects that had been ascribed to meaning frequency might actually be due to differences in associative strength. These results are discussed in terms of J. A. Fodor's (1983; 1990) "anti-semantic" modularity view. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring cerebral asymmetries for the verb generation task.

This study investigated potential right hemisphere involvement in the verb generation task. Six divided visual field experiments explored cerebral asymmetries for word retrieval in the verb generation task as well as in rhyme generation and immediate and delayed word pronunciation. The typical right visual field/left hemisphere (RVF/LH) advantage was observed for pronunciation and rhyme generation. For verb generation, the RVF/LH advantage was obtained only when stimulus items had a single prepotent response and not when there were multiple response alternatives. A semantic priming experiment suggested that activation for less common, related verbs was maintained for a longer time course within the right than within the left hemisphere. The authors suggest that the right hemisphere may play a role in continued activation of semantically related response alternatives in word generation and discuss methodological implications of their findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of left frontal lesions on the selection of context-appropriate meanings.

The present study examined the role of the left frontal cortex in strategic aspects of semantic processing. Participants were tested in a semantic priming task involving the meaning access of ambiguous and unambiguous words. Patients with left or bilateral frontal lesions failed to develop semantic facilitation of context-appropriate homograph meanings relative to age-matched controls. When the ambiguous words, however, were replaced by unambiguous words, patients with left frontal lesions improved to normal levels of semantic priming. This pattern of results seems difficult to explain in terms of a problem to access semantic information per se or to use contextual cues. The findings are, however, consistent with a deficit in selecting context-appropriate meanings in the presence of competing meanings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unconscious priming of association judgments.

Participants judged whether pairs of target words were associated or not-associated in meaning (association judgment task). Target pairs were preceded by a brief (200 ms) related or unrelated (prime) word presented to the nondominant eye. Each participant performed 2 blocks of association judgment task trials: 1 with primes that were legible, and 1 with primes that were masked by a pattern simultaneously presented to the dominant eye. Across 2 experiments, significantly larger masked priming effects were observed for participants who could not detect priming words (low-d′ participants) than for participants who could partially see priming words (high-d′ participants). This result suggests that undetectable masked primes can activate word meaning and that conscious attempts to process masked primes may inhibit unconscious activation. Additionally, evidence is presented that supports claims that spreading activation is the crucial mechanism responsible for unconscious priming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resolution of lexical ambiguity: Evidence from an eye movement priming paradigm.

Subjects' eye movements were monitored while they read 2-sentence passages of text. A target-word region was defined in the 2nd sentence of each passage. During the initial 35 ms of a target region eye fixation, an ambiguous word was presented as a prime. A target word subsequently replaced the prime during the fixation. Priming was measured by comparing fixation times on targets preceded by semantically related versus unrelated ambiguous primes. The type of prior context (consistent vs. inconsistent), type of ambiguous prime (biased vs. balanced), and strength of instantiated meaning (dominant vs. subordinate) could all affect priming. Priming effects were only found when the prior context was consistent with the dominant sense of a biased ambiguous prime. The results are discussed in terms of models of ambiguity resolution: The data seem most consistent with a reordered access model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The time course of graphic, phonological, and semantic activation in Chinese character identification.

In reading, lexical form–form relations may be more reliable then form–meaning relations. Accordingly, phonological forms (activated by graphic forms) become actual constituents, rather than addenda, of word identification. These considerations suggest that access to phonological forms can precede meaning access in single-word reading in many circumstances. The time course of form and meaning activation during Chinese word reading was tested in 2 primed-naming experiments varying prime type and prime-target stimulus onset asynchrony (SOA). The results showed a sequence of facilitation over SOA: (a) graphic, (b) phonological, (c) semantic. Words with precise meanings produced more rapid semantic priming than words with vague meanings. Graphic prime facilitation at a 43-ms SOA gave way to inhibition at longer SOAs. The onset of graphic inhibition coincided with the onset of phonological facilitation, suggesting a single identification moment. The authors describe an interactive constituency model that accounts for the pattern of data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of Verbal Semantic Impairment in Left Hemisphere Epilepsy.

Fifty-two patients with partial epilepsy of left (n=30) or right (n=22) hemisphere origin were compared with 23 healthy subjects to explore the characteristics and mechanisms of verbal semantic deficits. Picture Naming, Picture Pointing, and the Semantic Questionnaire assessed semantic retrieval, comprehension, and judgment, respectively. In comparison with the controls and right hemisphere patients, the left hemisphere patients showed impairments on Picture Naming and the Semantic Questionnaire. On Picture Naming, the left hemisphere patients made significant omissions and intracategorical errors; on the Semantic Questionnaire, they made errors at superordinate and subordinate levels of information, they made more errors in relation to living than nonliving things, and there were significant associations between their Picture Naming and Semantic Questionnaire scores. In this population, the mixed profiles of semantic deficits suggests the coexistence of altered retrieval and information loss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age and rate of activation in semantic memory.

Two word-primed picture-naming experiments were carried out to test the hypothesis that rate of activation in semantic memory is slower for older adults than for young adults. The presence of priming effects, both positive and negative, was taken as evidence of activation. In Exp 1 there was no age difference in the time of onset of either facilitation or inhibition by primes. A computer simulation, based on a simple connectionist model, showed that slower processing would have only a minimal effect on the time of onset of priming effects under the assumptions of the model; however, offset of inhibition by primes would be delayed if processing rate were reduced. In Exp 2 older adults showed inhibition by primes over a longer interval than did young adults, which was taken as evidence that the general slowing associated with aging extends to the transmission of activation at the earliest levels of cognitive processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of unconscious priming: I. Response competition, not spreading activation.

Four experiments were conducted to replicate and expand upon A. G. Greenwald, S. C. Draine, and R. L. Abram's (1996) demonstration that unconsciously perceived priming words can influence judgments of other words. The present experiments manipulated 2 types of relationships between priming and target stimuli: (a) whether priming and target stimuli possess a preexisting semantic relationship (an affective relationship in Experiments 1, 2, and 4; an associative relationship in Experiment 3; and an animacy relationship in Experiment 4) and (b) whether the primes and targets produce the same response. Large priming effects were found only when the primes and targets possessed response compatibility. No residual effects for affective, animacy, or semantic relatedness were observed. Although these results strongly support the conclusion that word meaning can be unconsciously activated, they do not support the claim that the unconscious perception effects obtained in Greenwald et al.'s (1996) paradigm are caused by automatic spreading activation of word meaning. Instead, the results reported here are consistent with a claim that unconsciously perceived words automatically trigger response tendencies that facilitate or interfere with target responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)