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.     

Picture-name priming in the cerebral hemispheres: evidence for phonological access in the right hemisphere

This study investigated right hemisphere involvement in access to phonology, using a picture-naming priming paradigm where pictures and names of common objects printed in Japanese Kana were presented in succession to the same visual field or different visual fields with a stimulus onset asynchrony of 250 msec. A naming task was used for this purpose. The result showed that, when primes and targets were presented to the same visual field, facilitation for related pairs was observed in each hemisphere, with overall naming latencies being slower in the right hemisphere than in the left hemisphere. This result indicates that the prior access to phonology for a picture in the right hemisphere facilitates phonological activation of a word that names the picture in this hemisphere, suggesting that the right hemisphere is involved in access to phonology. On the other hand, when primes and targets were presented to different visual fields, there was no facilitation for related pairs with inhibition for unrelated pairs, irrespective of prime and target visual fields. It is suggested that this inhibition-dominant pattern of priming may occur due to homotopic inhibition processes proposed by N. D. Cook.     

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.     

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.     

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.     

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.     

Observing or producing a motor action improves later perception of biological motion: Evidence for a gender effect

Two experiments are presented addressing the issue of whether observing (visual priming) or producing (motor priming) a running activity during a very short period (30 s) facilitates the perception of the direction of a point-light runner embedded in a dense dynamical mask. Experiment 1 showed that perceptual judgements improved and response time increased in the visual priming compared to the neutral priming condition (video of a moving car) in which judgements were at random. Because this effect was observed for male participants only, we performed a second experiment with the aim of evaluating the role of gender congruency in the visual priming condition. Results confirmed the facilitation effect and demonstrated that this effect was strictly dependent on the gender congruency between the perceiver and the priming information. Moreover, we found that actually producing a motor activity similar to the one presented in the video sequence improved to the same extent participants’ judgement of the direction of the point-light runner, without any gender effect. As a whole, these findings argue in favour of common representation for the perception and the production of human movement and showed that the perception of biological motion can be improved by prior motor activity either performed or observed. However, the gender-dependent effect of visual priming suggested that motor repertoire differed in males and females.     

Amodal processing of visual speech as revealed by priming

This study investigated the linguistic processing of visual speech (video of a talker's utterance without audio) by determining if such has the capacity to prime subsequently presented word and nonword targets. The priming procedure is well suited for the investigation of whether speech perception is amodal since visual speech primes can be used with targets presented in different modalities. To this end, a series of priming experiments were conducted using several tasks. It was found that visually spoken words (for which overt identification was poor) acted as reliable primes for repeated target words in the naming, written and auditory lexical decision tasks. These visual speech primes did not produce associative or reliable form priming. The lack of form priming suggests that the repetition priming effect was constrained by lexical level processes. That priming found in all tasks is consistent with the view that similar processes operate in both visual and auditory speech processing.     

Lateralized repetition priming for familiar faces: Evidence for asymmetric interhemispheric cooperation

Repetition priming refers to facilitated recognition of stimuli that have been seen previously. Although a great deal of work has examined the properties of repetition priming for familiar faces, little has examined the neuroanatomical basis of the effect. Two experiments are presented in this paper that combine the repetition priming paradigm with a divided visual field methodology to examine lateralized recognition of familiar faces. In the first experiment participants were presented with prime faces unilaterally to each visual field and target faces foveally. A significant priming effect was found for prime faces presented to the right hemisphere, but not for prime faces presented to the left hemisphere. In Experiment 2, prime and target faces were presented unilaterally, either to the same visual field or to the opposite visual field (i.e., either within hemisphere or across hemispheres). A significant priming effect was found for the within right hemisphere condition, but not for the within left hemisphere condition, replicating the findings of the first experiment. Priming was also found in both of the across hemispheres conditions, suggesting that interhemispheric cooperation occurs to aid recognition. Taken in combination these experiments provide two main findings. First, an asymmetric repetition priming effect was found, possibly as a result of asymmetric levels of activation following recognition of a prime face, with greater priming occurring within the right hemisphere. Second, there is evidence for asymmetric interhemispheric cooperation with transfer of information from the right hemisphere to the left hemisphere to facilitate recognition.     

Lateralized repetition priming for familiar faces: Evidence for asymmetric interhemispheric cooperation

Repetition priming refers to facilitated recognition of stimuli that have been seen previously. Although a great deal of work has examined the properties of repetition priming for familiar faces, little has examined the neuroanatomical basis of the effect. Two experiments are presented in this paper that combine the repetition priming paradigm with a divided visual field methodology to examine lateralized recognition of familiar faces. In the first experiment participants were presented with prime faces unilaterally to each visual field and target faces foveally. A significant priming effect was found for prime faces presented to the right hemisphere, but not for prime faces presented to the left hemisphere. In Experiment 2, prime and target faces were presented unilaterally, either to the same visual field or to the opposite visual field (i.e., either within hemisphere or across hemispheres). A significant priming effect was found for the within right hemisphere condition, but not for the within left hemisphere condition, replicating the findings of the first experiment. Priming was also found in both of the across hemispheres conditions, suggesting that interhemispheric cooperation occurs to aid recognition. Taken in combination these experiments provide two main findings. First, an asymmetric repetition priming effect was found, possibly as a result of asymmetric levels of activation following recognition of a prime face, with greater priming occurring within the right hemisphere. Second, there is evidence for asymmetric interhemispheric cooperation with transfer of information from the right hemisphere to the left hemisphere to facilitate recognition.     

Priming of abstract letter identities in the letter match task

Previous studies of letter recognition have not found priming for abstract letter identities. We used a task that required participants to decide whether a target is the same or different from a reference letter presented in opposite case, which avoids the shortcomings of tasks used in previous studies. We found robust priming effects in this task, which were the same size for letter pairs that have similar visual features across case (e.g., c/C, x/X) and dissimilar features (e.g., a/A, b/B). Also, the pattern of priming was the same whether the prime was in the same or different case as the reference. We take these findings as evidence that abstract letter identities support priming in this task. We suggest that the same–different match task is a useful tool for studying representations used to support masked priming in letter recognition and with other stimuli with limited set size.     

Semantic additivity and semantic inhibition: dissociable processes in the cerebral hemispheres?

We report the results of two visual half-field semantic priming experiments using a high proportion of related trials to examine hemisphere asymmetries for semantic processes beyond those attributable to automatic meaning activation. Contrary to previous investigations, we obtained inhibition for unrelated trials in both visual fields. However, priming was additive (being greater for words related via category membership and association than for either single dimension) only when words were presented to the RVF/left hemisphere. A third experiment, using centrally presented stimuli, implied that semantic additivity should be attributed to post-access meaning comparisons and inhibition to the generation of semantic expectancies. These results suggest (1) that inhibition and additivity are potentially dissociable "controlled" semantic processes and (2) that the left hemisphere predominates for meaning integration across successively presented words. The availability of finely tuned meaning integration processes in the left hemisphere may contribute to its superiority in language processing, despite right hemisphere competence for some semantic operations.     

Priming T2 in a visual and auditory attentional blink task

Participants performed an attentional blink (AB) task including digits as targets and letters as distractors within the visual and auditory domains. Prior to the rapid serial visual presentation, a visual or auditory prime was presented in the form of a digit that was identical to the second target (T2) on 50% of the trials. In addition to the "classic" AB effect, an overall drop in performance on T2 was observed for the trials on which the stream was preceded by an identical prime from the same modality. No cross-modal priming was evident, suggesting that the observed inhibitory priming effects are modality specific. We argue that the present findings represent a special type of negative priming operating at a low feature level.     

Priming of abstract letter identities in the letter match task

Previous studies of letter recognition have not found priming for abstract letter identities. We used a task that required participants to decide whether a target is the same or different from a reference letter presented in opposite case, which avoids the shortcomings of tasks used in previous studies. We found robust priming effects in this task, which were the same size for letter pairs that have similar visual features across case (e.g., c/C, x/X) and dissimilar features (e.g., a/A, b/B). Also, the pattern of priming was the same whether the prime was in the same or different case as the reference. We take these findings as evidence that abstract letter identities support priming in this task. We suggest that the same-different match task is a useful tool for studying representations used to support masked priming in letter recognition and with other stimuli with limited set size.     

Perceptual size discrimination requires awareness and late visual areas: A continuous flash suppression and interocular transfer study

We applied continuous flash suppression (CFS) during an interocular transfer paradigm to evaluate the importance of awareness and the contribution of early versus late visual structures in size recognition. Specifically, we tested if size judgements of a visible target could be influenced by a congruent or incongruent prime presented to the same or different eye. Without CFS, participants categorised a target as “small” or “large” more quickly when it was preceded by a congruent prime – regardless of whether the prime and target were presented to the same or different eye. Interocular transfer enabled us to infer that the observed priming was mediated by late visual areas. In contrast, there was no priming under CFS, which underscores the importance of awareness. We conclude that awareness and late visual structures are important for size perception and that any subconscious processing of the stimulus has minimal effect on size recognition.     

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.     

Taking the “text” out of context effects in repetition priming of word identification

Repetition priming of masked word identification is reduced when initial exposure to target words is in a text rather than in a word list. We demonstrate that there is nothing special about the text context that reduces priming. In Experiment 1, target words read in normal text or in rapid serial visual presentation (RSVP) text--either coherent or scrambled--produced similarly reduced priming, relative to the same words read aloud in a list. In Experiment 2, the delay was decreased between study and test for words presented in text, but they still displayed less priming than did words presented in a study list and tested after an equivalent delay. In Experiment 3, presenting study list words in RSVP to prevent reading each word aloud diminished priming to the same level as that in the text context. We conclude that presenting a target in context prevents it from being encoded and responded to as distinctively as when presented in isolation.     

Effects of prime and target eccentricity on masked repetition priming

Three experiments examined the influence of briefly presented, pattern-masked prime stimuli on target word recognition at varying eccentricities. The prime was either the same word as the targets or a different word, and prime position varied horizontally from a central fixation point. The targets were either in the same location as the primes (Experiment 1A) or always centrally located (Experiments 1B and 2). In Experiment 1A, target word recognition showed a typical right visual field advantage, and priming effects diminished with increasing prime and target eccentricity. With centrally located targets, priming effects tended to be more constrained by prime location. After eye fixation location and prime visibility were controlled for (Experiment 2), a right visual field advantage for priming effects was also evident for central targets, suggesting an influence of endogenous attentional biases in masked repetition priming.     

Form-Specific Visual Priming in the Left and Right Hemispheres

Word fragment completion performance was examined for items that were presented in the same or different letter case at study and test. During the study phase words and nonwords were presented at central fixation, then during the test phase a divided visual field technique was used in which word fragments were presented briefly to the right hemisphere (left visual field) or the left hemisphere (right visual field). Previous research using the word stem completion task indicated that only the right hemisphere was sensitive to case changes in words from study to test. In contrast, the current results indicate that in the fragment completion task the priming effects for the test items presented to either hemisphere were greater when the fragments were in the same compared to different letter case at study and test. These results indicate that both hemispheres are capable of supporting form-specific visual implicit memory.