The role of attention and study time in explicit and implicit memory for unfamiliar visual stimuli

The effects of limited attentional resources and study time on explicit and implicit memory were studied using Schacter and Cooper’s possible and impossible objects in their recognition and object decision paradigm. In one experiment, when attention at study was limited by a flanking digits procedure, object recognition was diminished but object decision priming for possible objects was unaffected; in another experiment, limiting attention plus reducing stimulus study time impaired object recognition and eliminated object priming. Recognition memory and perceptual priming for previously unfamiliar visual stimuli were both influenced by attention, although to different degrees. The intervening variable of study time determined the degree to which priming was affected by attentional resources. These results support a limited capacity attentional model for both recognition and perceptual priming of unfamiliar visual stimuli, and they highlight the need for assessing the interaction of attentional resources and study time in explicit and implicit memory tasks.     

Effects of dividing attention during encoding on perceptual priming of unfamiliar visual objects

According to the distractor-selection hypothesis (Mulligan, 2003), dividing attention during encoding reduces perceptual priming when responses to non-critical (i.e., distractor) stimuli are selected frequently and simultaneously with critical stimulus encoding. Because direct support for this hypothesis comes exclusively from studies using familiar word stimuli, the present study tested whether the predictions of the distractor-selection hypothesis extend to perceptual priming of unfamiliar visual objects using the possible/impossible object decision test. Consistent with the distractor-selection hypothesis, Experiments 1 and 2 found no reduction in priming when the non-critical stimuli were presented infrequently and non-synchronously with the critical target stimuli, even though explicit recognition memory was reduced. In Experiment 3, non-critical stimuli were presented frequently and simultaneously during encoding of critical stimuli; however, no decrement in priming was detected, even when encoding time was reduced. These results suggest that priming in the possible/impossible object decision test is relatively immune to reductions in central attention and that not all aspects of the distractor-selection hypothesis generalise to priming of unfamiliar visual objects. Implications for theoretical models of object decision priming are discussed.     

Enhanced perceptual priming for neutral stimuli in a traumatic context: A pathway to intrusive memories?

Clinical observations suggest that re-experiencing symptoms are triggered by stimuli that are perceptually similar to those present shortly before the trauma or its worst moments. Two experiments investigated the possible role of perceptual priming in this phenomenon. Volunteers (N = 28, N = 62) watched a series of "traumatic" and neutral picture stories, and completed blurred object identification (priming) and recognition memory tasks. Neutral objects that immediately preceded the "traumatic" stories were more strongly primed, but not better recognised, than objects from neutral stories. Enhanced priming predicted subsequent re-experiencing symptoms. The results support the role of perceptual priming in re-experiencing.     

Perceptual priming is not a necessary consequence of semantic classification of pictures

Four experiments investigated how repetition priming of object recognition is affected by the task performed in the prime and test phases. In Experiment 1 object recognition was tested using both vocal naming and two different semantic decision tasks (whether or not objects were manufactured, and whether or not they would be found inside the house). Some aspects of the data were inconsistent with contemporary models of object recognition. Specifically, object priming was eliminated with some combinations of prime and test tasks, and there was no evidence of perceptual (as opposed to conceptual or response) priming in either semantic classification task, even though perceptual identification of the objects is required for at least one of these tasks. Experiment 2 showed that even when perceptual demands were increased by brief presentation, the inside task showed no perceptual priming. Experiment 3 showed that the inside task did not appear to be based on conceptual priming either, as it was not primed significantly when the prime decisions were made to object labels. Experiment 4 showed that visual sensitivity could be restored to the inside task following practice on the task, supporting the suggestion that a critical factor is whether the semantic category is preformed or must be computed. The results show that the visual representational processes revealed by object priming depend crucially on the task chosen.     

Negative priming of unattended part primes: Implications for models of holistic and analytic processing in object recognition

The “hybrid” model of object recognition (Hummel, 2001) proposes that unattended objects are processed holistically, while attended objects are processed both holistically and analytically. Supporting evidence for this claim was reported by Thoma, Hummel, and Davidoff (2004) who showed that, unlike whole object primes, unattended split object parts (presumed to require analytic processing) do not elicit repetition priming. Here we tested the generality of this finding by contrasting priming for whole and part prime stimuli as a function of prime informativeness and by modifying the design so that both unattended whole and part prime displays contained a single perceptual object. Unlike Thoma et al. (2004) the results showed negative (rather than an absence of) priming for unattended half object primes. These findings place new constraints on theoretical models of the role of attention in object recognition.     

Perceptual differentiation as a source of category effects in object processing: Evidence from naming and object decision

The locus of category effects in picture recognition and naming was examined in two experiments with normal subjects. Subjects carried out object decision (deciding whether the stimulus is a “real” object or not) and naming tasks with pictures of clothing, furniture, fruit, and vegetables. These categories are distinguished by containing either relatively many exemplars with similar perceptual structures (fruit and vegetables;structurally similar categories), or relatively few exemplars with similar perceptual structures (clothing and furniture;structurally dissimilar categories). In Experiment 1, responses to the stimuli from the structurally similar categories were slower than responses to stimuli from the structurally dissimilar categories, and this effect was larger in the naming than in the object decision task. Further, prior object decisions to stimuli from structurally similar categories facilitated their subsequent naming. In Experiment 2, we orthogonally manipulated object decision and naming as prime and target tasks, again with stimuli from the four categories. Category effects, with responses slower to objects from structurally similar categories, were again larger in naming than in object decision, and these category effects in naming were reduced by priming with both naming and object decision. We interpret the data to indicate that category effects in object naming can reflect visually based competition which is reduced by the preactivation of stored structural knowledge for objects.     

Enhanced perceptual priming for neutral stimuli in a traumatic context: A pathway to intrusive memories?

Clinical observations suggest that re-experiencing symptoms are triggered by stimuli that are perceptually similar to those present shortly before the trauma or its worst moments. Two experiments investigated the possible role of perceptual priming in this phenomenon. Volunteers (N = 28, N = 62) watched a series of “traumatic” and neutral picture stories, and completed blurred object identification (priming) and recognition memory tasks. Neutral objects that immediately preceded the “traumatic” stories were more strongly primed, but not better recognised, than objects from neutral stories. Enhanced priming predicted subsequent re-experiencing symptoms. The results support the role of perceptual priming in re-experiencing.     

The influence of task requirements on priming in object decision and matching

We argue that task requirements can be the determinant in generating different results in studies on visual object recognition. We investigated priming for novel visual objects in three implicit memory tasks. A study-test design was employed in which participants first viewed line drawings of unfamiliar objects and later made different decisions about structural aspects of the objects. Priming for both symmetric and asymmetric possible objects was observed in a task requiring a judgment of structural possibility. However, when the task was changed to one requiring a judgment of structural symmetry, only symmetric possible objects showed priming. Finally, in a matching task in which participants made a same-different judgment, only symmetric possible objects exhibited priming. These results suggest that an understanding of object representation will be most fruitful if it is based on careful analyses of both the task demands and their interaction(s) with encoding and retrieval processes.     

Enhanced perceptual priming for neutral stimuli occurring in a traumatic context: two experimental investigations

Intrusive memories in posttraumatic stress disorder are often triggered by stimuli that are perceptually similar to those present shortly before or during the trauma. The present study aims to examine the possible role of perceptual priming in this phenomenon. It further investigates whether the degree of perceptual priming is associated with dissociation and whether both perceptual priming and intrusive memories can be reduced through elaboration. Two experiments measured perceptual priming for neutral stimuli that immediately preceded a "traumatic" event. Volunteers (N=46, 92) watched a series of "traumatic" and neutral picture stories, and completed a blurred object identification (perceptual priming) memory task, and a recognition memory task. Participants in Experiment 1 were selected to score either high or low on the Trait Dissociation Questionnaire [Murray, Ehlers, & Mayou (2002). Dissociation and posttraumatic stress disorder: Two prospective studies of motor vehicle accident survivors. British Journal of Psychiatry, 180, 363-368]. They also completed a state dissociation measure in the session. Experiment 2 randomly allocated participants to an experimental condition designed to increase elaboration or to a control condition. This experiment also included a measure of intrusive memories. Both experiments found enhanced perceptual priming for the stimuli that immediately preceded the "traumatic" stories compared to those preceding neutral stories. Participants with high trait dissociation showed relatively stronger perceptual perceptual priming. The degree of perceptual priming for stimuli from the "traumatic" stories also correlated with state dissociation (Experiment 1). Experimental manipulation of the elaboration of the stories showed that elaboration reduced the enhanced perceptual priming effect and the relative probability of reexperiencing symptoms (Experiment 2). The results support the role of perceptual priming in intrusions after traumatic events.     

An Item specific Locus of Repetition Priming

Two principal types of account of repetition priming postulate either facilitation of activation of perceptual representations used in stimulus recognition, or retrieval of specific processing episodes as possible mechanisms by which the effect occurs; these make different predictions concerning the priming of two stimuli presented simultaneously. In Experiments 1-3, subjects made same/different decisions about picture-word stimulus pairs. Recombining the pairings of a subset of items between training and test encounters did not significantly reduce the benefit in response time from repetition, as compared to pairs repeated intact. Subjects were able to remember the pairings (Experiment 4), but this did not influence repetition priming. Instead, the memory representations underlying the priming of each item in a pair were independent. No priming was found between pictures seen at training and words at test, and vice versa (Experiment 5), indicating that representations underlying the repetition effect were domain-specific. In Experiment 6, stimuli were all from within the domain of object pictures. Again, recombining the pairings of items between training and test did not significantly reduce the benefit in response time from repetition, as compared to pairs repeated intact. These results reveal an item-specific locus for repetition priming, consistent with priming occurring within pre-semantic perceptual representation systems involved in item recognition. The findings pose problems for theories that argue that repetition effects result only from retrieval of entire processing episodes.     

Object- and feature-based priming in visual search

Two contrasting accounts for priming in visual search have been proposed. The main difference between the two is the level of perceptual processing at which the priming effects are assumed to occur, whether priming is assumed to operate through the selective facilitation of features or at the level of selection of objects for response. The aim of the experiments here was to contrast these accounts. In the first two experiments, observers performed a search for the odd diamond in the midst of two distractor diamonds. Each diamond had two colors, but the configurations of the colors within the diamonds were different for the two experiments in ways previously shown to lend themselves differently well to object formation. The results show that priming can be both feature- and object-based, depending on the topological properties of the stimuli. This was confirmed in a third experiment, in which a quite dissimilar stimulus set was used to address the same question, once again yielding similar results. We thus show that priming operates at various levels of perceptual processing, a result consistent with new findings from neuroimaging and neuropsychology.     

Dissociation of rapid response learning and facilitation in perceptual and conceptual networks of person recognition

Repetition priming is a prominent example of non‐declarative memory, and it increases the accuracy and speed of responses to repeatedly processed stimuli. Major long‐hold memory theories posit that repetition priming results from facilitation within perceptual and conceptual networks for stimulus recognition and categorization. Stimuli can also be bound to particular responses, and it has recently been suggested that this rapid response learning, not network facilitation, provides a sound theory of priming of object recognition. Here, we addressed the relevance of network facilitation and rapid response learning for priming of person recognition with a view to advance general theories of priming. In four experiments, participants performed conceptual decisions like occupation or nationality judgments for famous faces. The magnitude of rapid response learning varied across experiments, and rapid response learning co‐occurred and interacted with facilitation in perceptual and conceptual networks. These findings indicate that rapid response learning and facilitation in perceptual and conceptual networks are complementary rather than competing theories of priming. Thus, future memory theories need to incorporate both rapid response learning and network facilitation as individual facets of priming.     

Hemispheric differences in specificity effects in talker identification

In the visual domain, Marsolek and colleagues (1999, 2008) have found support for two dissociable and parallel neural subsystems underlying object and shape recognition: an abstract-category subsystem that operates more effectively in the left cerebral hemisphere (LH), and a specific-exemplar subsystem that operates more effectively in the right cerebral hemisphere (RH). Evidence of this asymmetry has been observed in priming specificity for linguistic (words, pseudoword forms) and nonlinguistic (objects) stimuli. In the auditory domain, the authors previously found hemispheric asymmetries in priming effects for linguistic (spoken words) and nonlinguistic (environmental sounds) stimuli. In the present study, the same asymmetrical pattern was observed in talker identification by means of two long-term repetition-priming experiments. Both experiments consisted of a familiarization phase and a final talker identification test phase, using sentences as stimuli. The results showed that specificity effects (an advantage for same-sentence priming, relative to different-sentence priming) emerged when the target stimuli were presented to the left ear (RH), but not when the target stimuli were presented to the right ear (LH). Taken together, this consistent asymmetrical pattern of data from both domains-visual and auditory-may be indicative of a more general property of the human perceptual processing system. Theoretical implications are discussed.     

知觉信息先期呈现下两可图的命名和相似判断

在实物图片或轮廓图先期呈现的条件下研究了6岁、9岁、12岁及成人被试对两可图形的命名或相似判断。结果表明：（1）命名项目或相似判断与线索项目有关时,各年龄被试对判断项的命名或相似判断均表现出与线索项目一致的倾向。（2）轮廓图作为线索项目时．命名或相似判断反应时较长;实物作为线索项目时,命名或相似判断反应时较短。无关项目作为为线索项目时．被试命名或相似判断的反应时居中;命名项目或相似判断项目均与线索项目一致时反应时较短;命名项目或相似判断项目均与线索项目不一致时反应时延长。（3）被试命名或相似判断的反应时随其年龄的增长而下降,6岁和9岁儿童的反应时较长;12岁儿童的反应时较短;成人的反应时最短。     

Attention and perceptual implicit memory: effects of selective versus divided attention and number of visual objects

Extant research presents conflicting results on whether manipulations of attention during encoding affect perceptual priming. Two suggested mediating factors are type of manipulation (selective vs divided) and whether attention is manipulated across multiple objects or within a single object. Words printed in different colors (Experiment 1) or flanked by colored blocks (Experiment 2) were presented at encoding. In the full-attention condition, participants always read the word, in the unattended condition they always identified the color, and in the divided-attention conditions, participants attended to both word identity and color. Perceptual priming was assessed with perceptual identification and explicit memory with recognition. Relative to the full-attention condition, attending to color always reduced priming. Dividing attention between word identity and color, however, only disrupted priming when these attributes were presented as multiple objects (Experiment 2) but not when they were dimensions of a common object (Experiment 1). On the explicit test, manipulations of attention always affected recognition accuracy.