多目标觉知范式检验视觉意识容量

采用一种新的多目标觉知范式检验视觉意识容量。实验中首先迅速呈现包含8个刺激的圆形阵列（刺激位置随机分布）,然后所有刺激被灰色的圆覆盖,并随机选取阵列中的一个刺激作为目标,要求被试用尽可能少的点击次数找到目标。结果发现,即使被试不能一次击中目标,其也可能拥有对目标不精确的视觉信息。这些不精确的视觉信息能够帮助被试用更少的点击次数和更短的点击距离找到目标,且被试对这些不精确的视觉信息是有意识的。研究结果表明视觉意识能够以概率性的表征存在,并支持视觉整体统计假说,也能够进一步解释视觉意识容量的主观测量和客观测量之间存在的冲突。     

Why is information displaced from visual working memory during visual search?

Research has shown that performing visual search while maintaining representations in visual working memory displaces up to one object's worth of information from memory. This memory displacement has previously been attributed to a nonspecific disruption of the memory representation by the mere presentation of the visual search array, and the goal of the present study was to determine whether it instead reflects the use of visual working memory in the actual search process. The first hypothesis tested was that working memory displacement occurs because observers preemptively discard about an object's worth of information from visual working memory in anticipation of performing visual search. Second, we tested the hypothesis that on target absent trials no information is displaced from visual working memory because no target is entered into memory when search is completed. Finally, we tested whether visual working memory displacement is due to the need to select a response to the search array. The findings rule out these alternative explanations. The present study supports the hypothesis that change-detection performance is impaired when a search array appears during the retention interval due to nonspecific disruption or masking.     

Masked blindsight in normal observers: Measuring subjective and objective responses to two features of each stimulus

Recent visual masking studies that have measured visual awareness with graded subjective scales have often failed the show any evidence for unconscious visual processing in normal observers in a paradigm similar to that used in studies on blindsight patients. Without any reported awareness of the target, normal observers typically cannot discriminate target’s features better than chance. The present study examined processing of color and orientation by measuring graded awareness and forced-choice discriminations for both features in each trial. When no awareness for either feature was reported, discrimination of each feature succeed better than expected by chance, even when the other feature was incorrectly discriminated in the same trial. However, the characteristics of the mask determined whether or not masked blindsight was observed. We conclude that when the processing channels are free from intra-channel interference, unbound or weakly bound features can guide behaviour without any reported awareness in normal observers.     

Attentional capture by irrelevant color singletons

Four experiments investigated attentional capture by a color singleton in visual search for a nonsingleton target. B. S. Gibson and E. M. Kelsey (1998) found that a color singleton in a precuing array facilitated target discrimination at that location if the same color also signaled the target array onset. The authors found similar cuing effects regardless of whether the singleton color matched the target array and regardless of whether subjects could anticipate the singleton or target-array color. In Experiment 4, a color singleton captured attention when it appeared in the precuing array but not when it appeared in the target array. The results indicate that attentional control settings for displaywide attributes are imprecise: Although subjects may anticipate a specific color, they cannot avoid attentional capture by other irrelevant colors. In addition, the effect of irrelevant singletons depends on whether a target is simultaneously present in the array.     

The influence of visual search efficiency on the time-course of identity-based SR-compatibility

Three experiments were conducted to investigate the impact of stimulus-driven control on the time-course of stimulus-response (SR) compatibility. Participants responded to the presence or absence of a singleton arrow that was presented among multiple nontargets. When the singleton arrow was present, observers pressed a button with their right index finger, when it was absent they pressed with their left-index finger. SR-compatibility depended on the relation between the identity of the target and the present response: Even though the identity of the target singleton arrow (whether it was pointing to the right or left) was irrelevant to the task, the direction could be corresponding (right arrow) or noncorresponding (left arrow) with a target present response (the right hand). To examine the time-course of performance target-distractor similarity was varied to increase or decrease visual search efficiency and accordingly response latency. There were three main findings. First, the results of Experiment 1 showed that observers were no faster to respond 'present' when the singleton arrow pointed to the right (corresponding to the right hand) than when it pointed left (noncorresponding to the right hand) in a simple present-absent detection task. Second, only when observers were encouraged to process the identity of the arrow singleton, an effect of an SR-compatibility effect was found which developed over time. Third, the time-course of SR-compatibility was not influenced by visual search efficiency. The results of the present work suggest that visual selection and response selection occur in different stages.     

Identification of visual stimuli is improved by accompanying auditory stimuli: the role of eye movements and sound location

Can auditory signals influence the processing of visual information? The present study examined the effects of simple auditory signals (clicks and noise bursts) whose onset was simultaneous with that of the visual target, but which provided no information about the target. It was found that such a signal enhances performance in the visual task: the accessory sound reduced response times for target identification with no cost to accuracy. The spatial location of the sound (whether central to the display or at the target location) did not modify this facilitation. Furthermore, the same pattern of facilitation was evident whether the observer fixated centrally or moved their eyes to the target. The results were not altered by changes in the contrast (and therefore visibility) of the visual stimulus or by the perceived utility of the spatial location of the sound. We speculate that the auditory signal may promote attentional 'disengagement' and that, as a result, observers are able to process the visual target sooner when sound accompanies the display relative to when visual information is presented alone.     

Bottom-up and top-down control in visual search

Previous research suggests that the allocation of attention is largely controlled either in a stimulus-driven or in a goal-driven manner. To date, few studies have systematically manipulated variables affecting stimulus-driven and goal-driven selection independently in order to investigate how both manners of control interrelate and affect performance in visual search. In the present study observers were presented with search displays consisting of an array of line segments rotated at various orientations. The task of observers was to indicate the presence or absence of a vertical line segment (the target) presented amongst a series of nontargets and possibly one distractor. By varying the absolute differences in orientation between the target, nontargets, and distractors, relative target-distractor salience and target-distractor similarity were independently manipulated to investigate the contribution of stimulus-driven and goal-driven control. The major result was that relative target-distractor salience and target-distractor similarity affected search performance independently. Performance was better in cases where the irrelevant distractor was not a salient item in the search display and did not look similar to the target. The results are discussed in terms of models of attentional control.     

Basic processes in reading: Is visual word recognition obligatory?

Visual word recognition is commonly argued to be automatic in the sense that it is obligatory and ballistic. The present experiments combined Stroop and visual search paradigms to provide a novel test of this claim. An array of three, five, or seven words including one colored target (a word in Experiments 1 and 2, a bar in Experiment 3) was presented to participants. An irrelevant color word also appeared in the display and was either integrated with or separated from the colored target. The participants classified the color of the single colored item in Experiments 1 and 3 and determined whether a target color was present or absent in Experiment 2. A Stroop effect was observed in Experiment 1 when the color word and the color target were integral, but not when the color word and the color target were separated. No Stroop effect was observed in Experiment 2. Visual word recognition is contingent on both the distribution of spatial attention and task demands.     

Relative salience affects the process of detecting changes in orientation and luminance

This study tests the effect of relative saliency on perceptual comparison and decision processes in the context of change detection in which distinct visual mechanisms process two features (e.g., luminance and orientation). Townsend and Nozawa's (1995) systems factorial technology was used to investigate the process architecture and stopping rule when deciding whether luminance or orientation of a Gabor patch had changed. Experiment 1 found individual differences in decision strategies when we did not control relative saliency. One group of participants adopted co-active processing, and the other group adopted serial self-terminating processing to detect the change signals. When Experiment 2 eliminated the relative saliency, all but one observer adopted parallel processing and followed a self-terminating rule. These results support the relative saliency hypothesis and highlight the fact that observers adopt different change-detection strategies for two features, especially when relative saliency exists between the two feature dimensions.     

Localized attentional interference affects object individuation, not feature detection

Modern theorists conceptualize visual selective attention as a competition between object representations for the control of extrastriate receptive fields, an account supported by the finding that attentional selection of one stimulus can degrade processing of nearby stimuli. In the present study the conditions that produce reciprocal interference between attended stimuli are examined. Each display contained either no, one, or two feature-defined target items among an array of homogeneous distractors. Observers performed two tasks, feature detection and object individuation. The feature-detection task required observers to determine if any targets were present within the display. The object-individuation task required observers to determine if the number of targets was exactly two. Spatially mediated interference between target pairs occurred in the object-individuation task, but had no effect on feature detection. Results suggest that localized interference between attended stimuli occurs only when observers are required to resolve the features of individual objects, consistent with the competitive interaction models of attention.     

Contextual cuing by global features

In visual search tasks, attention can be guided to a target item--appearing amidst distractors--on the basis of simple features (e.g., finding the red letter among green). Chun and Jiang's (1998) contextual cuing effect shows that reaction times (RTs) are also speeded if the spatial configuration of items in a scene is repeated over time. In the present studies, we ask whether global properties of the scene can speed search (e.g., if the display is mostly red, then the target is at location X). In Experiment 1A, the overall background color of the display predicted the target location, and the predictive color could appear 0, 400, or 800 msec in advance of the search array. Mean RTs were faster in predictive than in nonpredictive conditions. However, there was little improvement in search slopes. The global color cue did not improve search efficiency. Experiments 1B-1F replicated this effect using different predictive properties (e.g., background orientation-texture and stimulus color). The results showed a strong RT effect of predictive background, but (at best) only a weak improvement in search efficiency. A strong improvement in efficiency was found, however, when the informative background was presented 1,500 msec prior to the onset of the search stimuli and when observers were given explicit instructions to use the cue (Experiment 2).     

Informative cues can slow search: The cost of matching a specific template

During visual search, observers hold in mind a search template, which they match against the stimulus. To characterize the content of this template, we trained observers to discriminate a set of artificial objects at an individual level and at a category level. The observers then searched for the objects on backgrounds that camouflaged the features that defined either the object’s identity or the object’s category. Each search stimulus was preceded by the target’s individual name, its category name, or an uninformative cue. The observers’ task was to locate the target, which was always present and always the only figure in the stimulus. The results showed that name cues slowed search when the features associated with the name were camouflaged. Apparently, the observers required a match between their mental representation of the target and the stimulus, even though this was unnecessary for the task. Moreover, this match involved all distinctive features of the target, not just the features necessary for a definitive identification. We conclude that visual search for a specific target involves a verification process that is performed automatically on all of the target’s distinctive features.     

Multiple attentional sets while monitoring rapid serial visual presentations

The present study examined whether observers are able to establish multiple attentional sets to concurrently monitor two different spatial locations. Observers identified a target letter in red or cyan among nontarget letters of other heterogeneous colours during a temporal feature search. A peripheral distractor display consisted of one item of either the same colour as the current target, and the other potential target colour, or an irrelevant colour that could never be the target. They identified an odd-ball colour letter among homogenous colours during a singleton search. The results revealed that observers maintained multiple attentional sets for detecting two singletons or for targets involving two (or three) features. However, they were unable to maintain a mixture of sets. Moreover, exposure to a distractor containing feature that corresponded to a feature of the current target was advantageous for target identification. The presence or absence of this set-specific capture depended on top-down knowledge and did not occur automatically in the singleton-detection stream. These results demonstrate a limitation in the flexibility of attentional sets. Although two singleton detections were possible, multiple attentional templates for a more complex attentional set could not be maintained concurrently when monitoring multiple rapid serial visual presentations.     

Effects of gravitational and optical stimulation on the perception of target elevation

To examine the combined effects of gravitational and optical stimulation on perceived target elevation, we independently altered gravitational-inertial force and both the orientation and the structure of a background visual array. While being exposed to 1.0, 1.5, or 2.0 Gz in the human centrifuge at NASA Ames Research Center, observers attempted to set a target to the apparent horizon. The target was viewed against the far wall of a box that was pitched at various angles. The box was brightly illuminated, had only its interior edges dimly illuminated, or was kept dark. Observers lowered their target settings as Gz was increased; this effect was weakened when the box was illuminated. Also, when the box was visible, settings were displaced in the same direction as that in which the box was pitched. We attribute our results to the combined influence of otolith-oculomotor mechanisms that underlie the elevator illusion and visual-oculomotor mechanisms (optostatic responses) that underlie the perceptual effects of viewing pitched visual arrays.     

Auditory attention causes visual inattentional blindness

When engaged in a visual task, we can fail to detect unexpected events that would otherwise be very noticeable. Here we ask whether a common auditory task, such as that of attending to a verbal stream, can also make us blind to the presence of visual objects that we do not anticipate. In two experiments, one hundred and twenty observers watched a dynamic display while performing either a visual or an auditory attention task, or both simultaneously. When observers were listening to verbal material, in order to either understand it or to remember it (auditory task), their probability of detecting an unexpected visual object was no higher than when they were counting bounces of moving items (visual task), although in the former case the observers' eyes and attention could move around the display freely rather than remaining focused on tracked items. Previous research has shown that attending to verbal material does not affect responses to lights flashing at irregular intervals, suggesting that driving performance is not hampered by listening. The lights, however, were expected. Our data imply that listening to the radio while driving, or to a portable audio player while walking or biking, can impair our reactions to objects or events that we do not expect.     

Cross-task repetition amnesia: Impaired recall of RSVP targets held in memory for a secondary task

People often fail to select and encode the second of two targets presented within less than 500ms in rapid serial visual presentation (RSVP), an effect known as the attentional blink. We investigated how report of the two targets is affected when one of them is maintained in working memory for a secondary, memory-search task. The results showed that report of either target was impaired when it was a member of the memory set relative to when it was not. This effect was independent of both the temporal interval separating the RSVP target from the presentation of the memory set and the interval separating the targets. We propose that the deficit in recall occurs because the association between a target and the memory-search task interferes with the formation of a new association between that target and the following RSVP task, with the result that observers may be biased to ascribe the target only to the memory set.     

Color singleton pop-out does not always poop out: An alternative to visual search

Folk psychology suggests that when an observer views a scene, a unique item will stand out and draw attention to itself. This belief stands in contrast to numerous studies in visual search that have found that a unique target item (e.g., a unique color) is not identified more quickly than a nonunique target. We hypothesized that this finding is the result of task demands of visual search, and that when the task does not involve visual search, uniqueness will pop out. We tested this hypothesis in a task in which observers were presented an array of letters and asked to respond aloud, as quickly as possible, with the identity of any one of the letters. The observers were significantly more likely to respond with a uniquely colored letter than would be expected by chance. In a task in which observers blurt out the first thing that they see, unique pop-out does not poop out.     

Attentional control settings modulate susceptibility to the induced Roelofs effect

When a visible frame is offset laterally from an observer's objective midline, the subjective midline is pulled toward the frame's center, causing the frame and any enclosed targets to be misperceived as being shifted somewhat in the opposite direction. This illusion, the Roelofs effect, is driven by environmental (bottom-up) visual cues, but whether it can be modulated by top-down (e.g., task-relevant) information is unknown. Here, we used an attentional manipulation (i.e., the color-contingency effect) to test whether attentional filtering can modulate the magnitude of the illusion. When observers were required to report the location of a colored target, presented within an array of differently colored distractors, there was a greater effect of the illusion when the Roelofs-inducing frame was the same color as the target. These results indicate that feature-based attentional processes can modulate the impact of contextual information on an observer's perception of space.     

Greater visual averaging of face identity for own-gender faces

Recent evidence suggests that observers can rapidly form an average representation based on a set of simultaneously presented faces. Here, we replicate this finding and show that the tendency to process sets of faces in terms of an average representation is greater for own-gender faces. Male and female participants viewed sets of four male or female faces before deciding whether or not a subsequently presented single test face had been present in the set. Incorrect endorsement that it was one of the set members was greater when the test face was a morphed average of the four faces than when it was an actual set member, and this effect was strongest when the gender of the faces was the same as the observer’s. The finding that observers were more likely to incorrectly endorse own-gender (vs. other-gender) faces forms an exception to the often reported own-gender advantage in face recognition.     

Vicariously Learned Helplessness: The Role of Perceived Dominance and Prestige of a Model

Prior research has examined the relationship between various model characteristics (e.g., age, competence, similarity) and the likelihood that the observers will experience vicariously learned helplessness. However, no research in this area has investigated dominance as a relevant model characteristic. This study explored whether the vicarious acquisition of learned helplessness could be mediated by the perceived dominance of a model. Participants observed a model attempting to solve anagrams. Across participant groups, the model displayed either dominant or nondominant characteristics and was either successful or unsuccessful at solving the anagrams. The characteristics displayed by the model significantly affected observers’ ratings of his dominance and prestige. After viewing the model, participants attempted to solve 40 anagrams. When the dominant model was successful, observers solved significantly more anagrams than when he was unsuccessful. This effect was not found when the model was nondominant.