Automatic semantic priming in the left and right hemispheres

We investigated hemispheric differences and inter-hemispheric transfer of facilitation in automatic semantic priming, using prime-target pairs composed of words of the same category but not associated (e.g. skirt-glove), and a blank-target baseline condition. Reaction time and accuracy were measured at short (300 ms) intervals between prime and target onsets, using a go/no-go task to discriminate between word or non-word targets. Reaction times were facilitated more for target words presented in the right visual field (RVF) compared to the left visual field (LVF), and targets presented in RVF were primed in both visual fields, whereas targets presented in LVF were primed by primes in the LVF only. These results suggest that both hemispheres are capable of automatic priming at very short stimulus onset asymmetries (SOA), but cross-hemisphere priming occurs only in the left hemisphere.     

Semantic and associative priming in the cerebral hemispheres: some words do, some words don't ... sometimes, some places

This study investigated spreading activation for words presented to the left and right hemispheres using an automatic semantic priming paradigm. Three types of semantic relations were used: similar-only (Deer-Pony), associated-only (Bee-Honey), and similar + associated (Doctor-Nurse). Priming of lexical decisions was symmetrical over visual fields for all semantic relations when prime words were centrally presented. However, when primes and targets were lateralized to the same visual field, similar-only priming was greater in the LVF than in the RVF, no priming was obtained for associated-only words, and priming was equivalent over visual fields for similar + associated words. Similar results were found using a naming task. These findings suggest that it is important to lateralize both prime and target information to assess hemisphere-specific spreading activation processes. Further, while spreading activation occurs in either hemisphere for the most highly related words (those related by category membership and association), our findings suggest that automatic access to semantic category relatedness occurs primarily in the right cerebral hemisphere. These results imply a unique role for the right hemisphere in the processing of word meanings. We relate our results to our previous proposal (Burgess & Simpson, 1988a; Chiarello, 1988c) that there is rapid selection of one meaning and suppression of other candidates in the left hemisphere, while activation spreads more diffusely in the right hemisphere. We also outline a new proposal that activation spreads in a different manner for associated words than for words related by semantic similarity.     

Masked repetition and phonological priming in picture naming

We report a series of picture naming experiments in which target pictures were primed by briefly presented masked words. Experiment 1 demonstrates that the prior presentation of the same word prime (e.g.,rose-rose) facilitates picture naming independently of the target’s name frequency. In Experiment 2, primes that were homophones of picture targets (e.g.,rows-rose) also produced facilitatory effects compared with unrelated controls, but priming was significantly larger for targets with low-frequency names relative to targets with high-frequency names. In Experiment 3, primes that were higher frequency homophones of picture targets produced facilitatory effects compared with identical primes. These results are discussed in relation to different accounts of the effects of masked priming in current models of picture naming.     

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.     

Hemispheric differences in the time-course of semantic priming processes: evidence from event-related potentials (ERPs)

To investigate hemispheric differences in the timing of word priming, the modulation of event-related potentials by semantic word relationships was examined in each cerebral hemisphere. Primes and targets, either categorically (silk-wool) or associatively (needle-sewing) related, were presented to the left or right visual field in a go/no-go lexical decision task. The results revealed significant reaction-time and physiological differences in both visual fields only for associatively related word pairs, but an electrophysiological difference also tended to reach significance for categorically related words when presented in the left visual field. ERP waveforms showed a different time-course of associative priming effects according to the field of presentation. In the right visual field/left hemisphere, both N400 and Late Positive Component (LPC/P600) were modulated by semantic relatedness, while only a late effect was present in the left visual field/ right hemisphere.     

Semantic priming over unrelated trials: Evidence for different effects in word and picture naming

Two naming experiments are reported that replicated previous findings of semantic interference as a result of naming related word or picture primes three trials before picture targets. We also examined whether semantic interference occurred when the materials were reversed and picture or word primes were named before word targets. The interest in semantic interference during word naming followed a suggestion made by Humphreys, Lloyd-Jones, and Fias (1995) that word naming, like picture naming, may be reliant on a semantic route to name retrieval when the two stimuli are mixed. In contrast to their findings, we found no evidence for semantic interference during target word naming; in fact, we found facilitation from related picture primes. No priming was found for the related word prime and word target condition. The data allow us to rule out the possibility that word naming is reliant on a semantic route when mixed with pictures in this priming paradigm and to conclude that there is no clear evidence of semantic activation during word naming. We also conclude, in line with other research, that word naming and picture naming involve different processes.     

Right hemispheric dominance in processing of unconscious negative emotion

Right hemispheric dominance in unconscious emotional processing has been suggested, but remains controversial. This issue was investigated using the subliminal affective priming paradigm combined with unilateral visual presentation in 40 normal subjects. In either left or right visual fields, angry facial expressions, happy facial expressions, or plain gray images were briefly presented as negative, positive, and control primes, followed by a mosaic mask. Then nonsense target ideographs were presented, and the subjects evaluated their partiality toward the targets. When the stimuli were presented in the left, but not the right, visual fields, the negative primes reduced the subjects' liking for the targets, relative to the case of the positive or control primes. These results provided behavioral evidence supporting the hypothesis that the right hemisphere is dominant for unconscious negative emotional processing.     

Right hemispheric dominance in processing of unconscious negative emotion

Right hemispheric dominance in unconscious emotional processing has been suggested, but remains controversial. This issue was investigated using the subliminal affective priming paradigm combined with unilateral visual presentation in 40 normal subjects. In either left or right visual fields, angry facial expressions, happy facial expressions, or plain gray images were briefly presented as negative, positive, and control primes, followed by a mosaic mask. Then nonsense target ideographs were presented, and the subjects evaluated their partiality toward the targets. When the stimuli were presented in the left, but not the right, visual fields, the negative primes reduced the subjects’ liking for the targets, relative to the case of the positive or control primes. These results provided behavioral evidence supporting the hypothesis that the right hemisphere is dominant for unconscious negative emotional processing.     

Masked priming is abstract in the left and right visual fields

Two experiments assessed masked priming for words presented to the left and right visual fields in a lexical decision task. In both Experiments, the same magnitude and pattern of priming was obtained for visually similar (kiss-KISS) and dissimilar (read-READ) prime-target pairs. These findings provide no support for the hypothesis that word identification is mediated by separate and lateralized abstract and specific visual form systems. Strikingly, equivalent priming was observed when primes and targets were presented to the same or opposite visual fields, suggesting that priming occurs after visual information from the two hemispheres is integrated.     

A right visual field advantage for visual processing of manipulable objects

Information about object-associated manipulations is lateralized to left parietal regions, while information about the visual form of tools is represented bilaterally in ventral occipito-temporal cortex. It is unknown how lateralization of motor-relevant information in left-hemisphere dorsal stream regions may affect the visual processing of manipulable objects. We used a lateralized masked priming paradigm to test for a right visual field (RVF) advantage in tool processing. Target stimuli were tools and animals, and briefly presented primes were identical to or scrambled versions of the targets. In Experiment 1, primes were presented either to the left or to the right of the centrally presented target, while in Experiment 2, primes were presented in one of eight locations arranged radially around the target. In both experiments, there was a RVF advantage in priming effects for tool but not for animal targets. Control experiments showed that participants were at chance for matching the identity of the lateralized primes in a picture?Cword matching experiment and also ruled out a general RVF speed-of-processing advantage for tool images. These results indicate that the overrepresentation of tool knowledge in the left hemisphere affects visual object recognition and suggests that interactions between the dorsal and ventral streams occurs during object categorization.     

Probing hemispheric processes in an on-line reading task

Coney (1998) used a priming procedure to obtain evidence that the left and right hemispheres contributed equally to lexical processing of concrete nouns in a continuous reading task. In that study, however, there was no direct validation of the involvement of the right hemisphere in the task, and the possibility of left hemisphere processing of left visual field target stimuli could not be ruled out. The present study was designed to obtain validating evidence by using abstract and concrete noun primes in a similar reading task on the assumption that if the right hemisphere was contributing to the task there would be demonstrable differences between the visual fields in processing targets primed by abstract nouns. The results supported this expectation. While concrete targets projected to each visual field were primed by concrete nouns, there was significant priming by abstract nouns only in respect of targets presented to the right visual field. It is argued that this finding supports the involvement of the right hemisphere in continuous reading and further delimits the scope of its contribution to this process. Somewhat unexpectedly, the results also revealed that absolute response times were faster to left visual field targets when they were preceded by abstract nouns, even when there was no semantic relationship between the two words. It was suggested that this effect derives from the inability of the right hemisphere to process abstract nouns in that the failure of abstract nouns to engage lexical processing mechanisms leaves the right hemisphere relatively unencumbered when required to process a subsequent target.     

Access to concrete word meanings in the cerebral hemispheres: facilitation and inhibition effects

In 2002 Shibahara and Lucero-Wagoner, using a priming paradigm, reported a larger facilitation for concrete noun pairs in the right than left hemisphere when the stimulus onset asynchrony was 250 msec. Their related prime-target pairs were similar not only in meaning but also perceptual attributes, such as shape. They had reported such perceptual information to be available only in the right hemisphere early in target processing. Thus, we predicted that, when the stimulus onset asynchrony is long, there would be no effect of perceptual information on target processing in the right hemisphere, resulting in no hemispheric differences in the amount of facilitation. We also predicted that target processing would be inhibited by prior presentation of unrelated primes only in the left hemisphere because inhibition seems to be produced by the attention system in the left hemisphere. The present experiment was designed to test these predictions, using the stimulus onset asynchrony of 550 msec. and the same prime-target pairs. Analysis showed no hemispheric differences in the amount of facilitation, and inhibition effects for unrelated pairs were produced in both hemispheres. It is suggested that the inhibition effects in each hemisphere might be produced by different mechanisms.     

Inhibition of return in subliminal letter priming

The present study combined exogenous spatial cueing with masked repetition priming to study attentional influences on the processing of subliminal stimuli. Participants performed an alphabetic decision task (letter versus pseudo-letter classification) with central targets and briefly presented peripherally located primes that were either cued or not cued by an abrupt onset. A relatively long delay between cue and prime was used to investigate the effect of inhibition of return (IOR) on the processing of subliminal masked primes. Primes presented to the left visual field showed standard effects of Cue Validity and no IOR (significant priming with valid cues only). Primes presented to the right visual field showed no priming from valid cues (an IOR effect), and priming with invalid cues that depended on hand of response to letter targets (right-hand in Experiment 1, left-hand in Experiment 2). The results are interpreted in terms of a differential speed of engagement and disengagement of attention to the right and left visual fields for alphabetic stimuli, coupled with a complex interaction that arises between Prime Relatedness and response-hand.     

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.     

Response-bound primes diminish affective priming in the naming task

We found affective priming in the naming task (i.e., faster naming of a target picture that follows a valence-congruent prime picture compared to an incongruent prime) significantly reduced if prime stimuli were strongly bound to a naming response compared to when primes did not elicit a naming response. This result indicates that affective priming in the naming task originates from encoding facilitation processes, which are usually overshadowed by response conflict due to primes that also trigger a naming response.     

Semantic interference and associative facilitation from words presented in rapid serial visual presentation

Semantic interference in picture naming is readily obtained when categorically related distractor words are displayed with picture targets; however, this is not typically the case when both primes and targets are words. Researchers have argued that to obtain semantic interference for word primes and targets, the prime must be shown for a sufficient duration, prime processing must be made difficult, and participants must attend to the primes. In this article, we used a novel procedure for prime presentation to investigate semantic interference in word naming. Primes were presented as the last word of a rapid serial visual presentation stream, with the target following 600-1,200 msec later. Semantic interference was observed for categorically related targets, whereas facilitation was found for associatively related targets.     

Masked priming is abstract in the left and right visual fields

Two experiments assessed masked priming for words presented to the left and right visual fields in a lexical decision task. In both Experiments, the same magnitude and pattern of priming was obtained for visually similar (kiss-KISS) and dissimilar (read-READ) prime–target pairs. These findings provide no support for the hypothesis that word identification is mediated by separate and lateralized abstract and specific visual form systems. Strikingly, equivalent priming was observed when primes and targets were presented to the same or opposite visual fields, suggesting that priming occurs after visual information from the two hemispheres is integrated.     

A study of masked form priming in picture and word naming

We report a series of picture- and word-naming experiments in which the masked priming paradigm with prime exposures brief enough to prevent prime identification were used. Experiment 1 demonstrates that the prior presentation of the same word prime facilitates both picture and word naming independently of target frequency. In Experiments 2 and 3, primes that were pseudohomophones of picture targets produced facilitatory effects compared with orthographic controls, but these orthographically similar nonword primes did not facilitate picture naming compared with unrelated controls. On the other hand, word targets were primarily facilitated by orthographic prime— target overlap. This marked dissociation in the priming effects obtained with picture and word targets is discussed in relation to different explanations of masked form priming effects in visual word recognition and current models of picture and word naming.     

Affective Priming Effects in the Left and Right Cerebral Hemispheres in Patients With Alzheimer's Disease

Alzheimer’s disease (AD) patients and control subjects were tested in an affective priming paradigm associated with an affective discrimination task. Two pictures, one affectively positive or affectively negative and the other neutral, were presented simultaneously in the right and in the left visual fields; the participants had to decide which of the two pictures was the most affectively positive or negative. The target pictures were preceded by a prime picture that was either affectively positive, affectively negative, or neutral. The principal result was the observation, in AD patients as well as in control subjects, of negative affective priming effects for targets presented in the right hemisphere, and of positive affective priming effects for targets presented in the left hemisphere. The presence of affective priming effects suggests that AD patients have no particular deficit in the automatic activation of emotional information; the fact that priming effects were also observed for targets presented in the left hemisphere showed that AD patients probably have no left hemisphere deficit in the automatic activation of emotional information. However, in AD patients, affective priming effects were significant with negative targets but not with positive targets, which could suggest that AD patients processed positive targets in a more semantic way than negative targets.     

Semantic priming with abstract and concrete words: differential asymmetry may be postlexical

We investigated whether abstract and concrete words would be differentially effective in priming lexical decisions to words presented to the right and left visual fields. Under low probability prime conditions, where priming is presumed to reflect a spreading activation process within the lexicon, equivalent priming was obtained in each VF for both abstract and concrete primes. However, when the same words were used in a high probability prime paradigm, abstract primes were much less effective in the LVF than in the RVF, while priming with concrete words did not differ across the visual fields. Since such priming may reflect a postlexical semantic integration stage, the results imply that hemisphere differences for processing abstract and concrete words may arise only after lexical access has occurred, when semantic information retrieved from the lexicon becomes available for subsequent processing.