视空工作记忆负载对场景主旨加工的影响

本研究采用工作记忆任务和场景辨别任务相结合的双任务范式探究客体工作记忆负载 (实验1)和空间工作记忆负载 (实验2) 对场景主旨辨别的影响。结果发现: (1) 与无负载条件相比, 客体负载条件下的非参辨别力指数(A’)明显下降, 而空间负载条件下A’无明显变化; (2) 随着场景图片呈现时间的延长, 场景辨别任务的A’逐渐提高; (3) 对自然场景和人工场景匹配情况下的A’ 明显高于对自然与自然或者人工与人工匹配情况下的A’。由此可见, 场景主旨识别, 特别是基本水平的场景主旨辨别, 与客体工作记忆共享部分认知资源, 而不与/很少与空间工作记忆共享认知资源; 在识别过程中, 上级水平范畴识别优先于基本水平范畴识别, 进一步支持了上级水平范畴优先的主旨层级加工观点。     

How Are Different Properties of a Scene Encoded in Visual Memory?

Recent studies in scene perception suggest that much of what observers believe they see is not retained in visual memory. Depending on the roles they play in organizing the perception of a scene, different visual properties may require different amounts of attention to be incorporated into a mental representation of the scene. The goal of this study was to compare how three visual properties of scenes, colour, object position, and object presence, are encoded in visual memory. We used a variation on the change detection “flicker” task and measured the time to detect scene changes when: (1) a cue was provided regarding the type of change; and, (2) no cue was provided. We hypothesized that cueing would enhance the processing of visual properties that require more attention to be encoded into scene representations, whereas cueing would not have an effect for properties that are readily or automatically encoded in visual memory. In Experiment 1, we found that there was a cueing advantage for colour changes, but not for position or presence changes. In Experiment 2, we found the same cueing effect regardless of whether the colour change altered the configuration of the scene or not. These results are consistent with the idea that properties that typically help determine the configuration of the scene, for example, position and presence, are better encoded in scene representations than are surface properties such as colour.     

The importance of information localization in scene gist recognition

People can recognize the meaning or gist of a scene from a single glance, and a few recent studies have begun to examine the sorts of information that contribute to scene gist recognition. The authors of the present study used visual masking coupled with image manipulations (randomizing phase while maintaining the Fourier amplitude spectrum; random image structure evolution [RISE]; J. Sadr & P. Sinha, 2004) to explore whether and when unlocalized Fourier amplitude information contributes to gist perception. In 4 experiments, the authors found that differences between scene categories in the Fourier amplitude spectrum are insufficient for gist recognition or gist masking. Whereas the global 1/f spatial frequency amplitude spectra of scenes plays a role in gist masking, local phase information is necessary for gist recognition and for the strongest gist masking. Moreover, the ability to recognize the gist of a target image was influenced by mask recognizability, suggesting that conceptual masking occurs even at the earliest stages of scene processing.     

大脑视知觉调控的神经机制

大脑的知觉加工并非单纯由外部刺激驱动,而是存在自上而下的知觉调控。尽管这一现象被大量实验研究证实,但其神经机制仍然是认知神经科学研究的重要问题。本研究系统介绍了知觉调控的神经基础、实现形式、研究范式,及其理论模型,分析指出了当前研究面临的主要问题,并对未来的研究进行了展望,以期促进该问题研究的进一步开展。     

Ultrafast scene detection and recognition with limited visual information

Humans can detect target colour pictures of scenes depicting concepts like picnic or harbour in sequences of six or 12 pictures presented as briefly as 13?ms, even when the target is named after the sequence. Such rapid detection suggests that feedforward processing alone enabled detection without recurrent cortical feedback. There is debate about whether coarse, global, low spatial frequencies (LSFs) provide predictive information to high cortical levels through the rapid magnocellular (M) projection of the visual path, enabling top-down prediction of possible object identities. To test the “Fast M” hypothesis, we compared detection of a named target across five stimulus conditions: unaltered colour, blurred colour, greyscale, thresholded monochrome, and LSF pictures. The pictures were presented for 13–80?ms in six-picture rapid serial visual presentation (RSVP) sequences. Blurred, monochrome, and LSF pictures were detected less accurately than normal colour or greyscale pictures. When the target was named before the sequence, all picture types except LSF resulted in above-chance detection at all durations. Crucially, when the name was given only after the sequence, performance dropped and the monochrome and LSF pictures (but not the blurred pictures) were at or near chance. Thus, without advance information, monochrome and LSF pictures were rarely understood. The results offer only limited support for the Fast M hypothesis, suggesting instead that feedforward processing is able to activate conceptual representations without complementary reentrant processing.     

Recognising the forest, but not the trees: an effect of colour on scene perception and recognition

Colour has been shown to facilitate the recognition of scene images, but only when these images contain natural scenes, for which colour is 'diagnostic'. Here we investigate whether colour can also facilitate memory for scene images, and whether this would hold for natural scenes in particular. In the first experiment participants first studied a set of colour and greyscale natural and man-made scene images. Next, the same images were presented, randomly mixed with a different set. Participants were asked to indicate whether they had seen the images during the study phase. Surprisingly, performance was better for greyscale than for coloured images, and this difference is due to the higher false alarm rate for both natural and man-made coloured scenes. We hypothesized that this increase in false alarm rate was due to a shift from scrutinizing details of the image to recognition of the gist of the (coloured) image. A second experiment, utilizing images without a nameable gist, confirmed this hypothesis as participants now performed equally on greyscale and coloured images. In the final experiment we specifically targeted the more detail-based perception and recognition for greyscale images versus the more gist-based perception and recognition for coloured images with a change detection paradigm. The results show that changes to images are detected faster when image-pairs were presented in greyscale than in colour. This counterintuitive result held for both natural and man-made scenes (but not for scenes without nameable gist) and thus corroborates the shift from more detailed processing of images in greyscale to more gist-based processing of coloured images.     

Describing scenes hardly seen

Knowledge about scene categories, the so-called gist, can be extracted very rapidly, while recognition and naming of individual scene objects is a more effortful process. We investigate this phenomenon by presenting action scenes involving two actors for durations varying between 100 and 300 ms. Incoherence was created by mirroring individual scene actors. Upon masked presentation participants had to report content, actors and objects and to indicate whether the scene was meaningful or not. Scene coherence was judged correctly at all presentation durations. Actors were correctly identified in about one-third of the cases even with presentation durations of 100 ms, and identification rate increased up to 80% with longer durations. Identification depended on scene coherence, on the position of agents in the scene, and on the position of actors relative to the fixation cross. These interdependencies of scene and object perception indicate that the visual system seems to be very sensitive to meaningful interactions of living entities. A series of fixations is not necessary to identify actors of a scene.     

上下文预期在快速场景识别中的作用

本研究首先考察上下文预期是否能够影响快速场景识别,进而通过比较不同空间频率的场景信息来探究上下文预期在快速场景识别不同阶段的作用。共包括3个实验:实验1采用双眼竞争范式,考察对快速呈现场景刺激的主观选择是否受到上下文预期的影响;实验2采用词汇分类与快速场景识别的双任务范式,比较预期与非预期条件下快速场景识别绩效的差异;实验3分别以低频信息(实验3a)和高频信息(实验3b)作为实验材料,探讨预期效应的作用阶段。结果发现:上下文预期可以影响快速场景识别过程中的主观选择与反应绩效;对不同空间频率的场景信息,场景刺激与预期相一致时均可以提高辨别力,但预期对反应偏好的影响只发生在对高空间频率场景信息的加工阶段。因此,上下文预期在快速场景识别不同加工阶段的作用不同,快速场景识别需要结合不同空间频率信息加工的结果。     

Is attention necessary for object identification? Evidence from eye movements during the inspection of real-world scenes

Eye movements were recorded during the display of two images of a real-world scene that were inspected to determine whether they were the same or not (a comparative visual search task). In the displays where the pictures were different, one object had been changed, and this object was sometimes taken from another scene and was incongruent with the gist. The experiment established that incongruous objects attract eye fixations earlier than the congruous counterparts, but that this effect is not apparent until the picture has been displayed for several seconds. By controlling the visual saliency of the objects the experiment eliminates the possibility that the incongruency effect is dependent upon the conspicuity of the changed objects. A model of scene perception is suggested whereby attention is unnecessary for the partial recognition of an object that delivers sufficient information about its visual characteristics for the viewer to know that the object is improbable in that particular scene, and in which full identification requires foveal inspection.     

The influence of color on the perception of scene gist

In 3 experiments the authors used a new contextual bias paradigm to explore how quickly information is extracted from a scene to activate gist, whether color contributes to this activation, and how color contributes, if it does. Participants were shown a brief presentation of a scene followed by the name of a target object. The target object could be consistent or inconsistent with scene gist but was never actually present in the scene. Scene gist activation was operationalized as the degree to which participants respond "yes" to consistent versus inconsistent objects, reflecting a response bias produced by scene gist. Experiment 1 demonstrated that scene gist is activated after a 42-ms exposure and that the strength of the activation increases with longer presentation durations. Experiments 2 and 3 explored the contribution of color to the activation of scene gist. The results revealed that color has an influence across a wide variety of scenes and is directly associated with scene gist.     

Top-down knowledge modulates onset capture in a feedforward manner

How do we select behaviourally important information from cluttered visual environments? Previous research has shown that both top-down, goal-driven factors and bottom-up, stimulus-driven factors determine which stimuli are selected. However, it is still debated when top-down processes modulate visual selection. According to a feedforward account, top-down processes modulate visual processing even before the appearance of any stimuli, whereas others claim that top-down processes modulate visual selection only at a late stage, via feedback processing. In line with such a dual stage account, some studies found that eye movements to an irrelevant onset distractor are not modulated by its similarity to the target stimulus, especially when eye movements are launched early (within 150-ms post stimulus onset). However, in these studies the target transiently changed colour due to a colour after-effect that occurred during premasking, and the time course analyses were incomplete. The present study tested the feedforward account against the dual stage account in two eye tracking experiments, with and without colour after-effects (Exp. 1), as well when the target colour varied randomly and observers were informed of the target colour with a word cue (Exp. 2). The results showed that top-down processes modulated the earliest eye movements to the onset distractors (<150-ms latencies), without incurring any costs for selection of target matching distractors. These results unambiguously support a feedforward account of top-down modulation.     

Feedforward and feedback consistency effects for high- and low-frequency words in lexical decision and naming

In three experiments, we examined feedforward and feedback consistency effects in word recognition. Feedforward consistency is the degree to which a word's pronunciation is consistent with that of similarly spelled words, and feedback consistency refers to whether there is more than one way to spell a pronunciation. Previously, Stone, Vanhoy, and Van Orden (1997) reported feedforward and feedback consistency effects for low-frequency words in a lexical decision task. We investigated the effect of feedforward and feedback consistency for both high- and low-frequency words in lexical decision and naming. In both tasks, we found that feedforward and feedback inconsistent words were processed more slowly than consistent words, regardless of word frequency. These findings indicate that both types of consistency are involved in visual word recognition.     

The relative contribution of scene context and target features to visual search in scenes

Many experiments have shown that knowing a targets visual features improves search performance over knowing the target name. Other experiments have shown that scene context can facilitate object search in natural scenes. In this study, we investigated how scene context and target features affect search performance. We examined two possible sources of information from scene context—the scenes gist and the visual details of the scene—and how they potentially interact with target-feature information. Prior to commencing search, participants were shown a scene and a target cue depicting either a picture or the category name (or no-information control). Using eye movement measures, we investigated how the target features and scene context influenced two components of search: early attentional guidance processes and later verification processes involved in the identification of the target. We found that both scene context and target features improved guidance, but that target features also improved speed of target recognition. Furthermore, we found that a scenes visual details played an important role in improving guidance, much more so than did the scenes gist alone.     

Natural-scene perception requires attention

Is visual attention required for visual consciousness? In the past decade, many researchers have claimed that awareness can arise in the absence of attention. This claim is largely based on the notion that natural scene (or "gist") perception occurs without attention. This article presents evidence against this idea. We show that when observers perform a variety of demanding, sustained-attention tasks, inattentional blindness occurs for natural scenes. In addition, scene perception is impaired under dual-task conditions, but only when the primary task is sufficiently demanding. This finding suggests that previous studies that have been interpreted as demonstrating scene perception without attention failed to fully engage attention and that natural-scene perception does indeed require attention. Thus, natural-scene perception is not a preattentive process and cannot be used to support the idea of awareness without attention.     

The role of higher order image statistics in masking scene gist recognition

In the present article, we investigated whether higher order image statistics, which are known to be carried by the Fourier phase spectrum, are sufficient to affect scene gist recognition. In Experiment 1, we compared the scene gist masking strength of four masking image types that varied in their degrees of second- and higher order relationships: normal scene images, scene textures, phase-randomized scene images, and white noise. Masking effects were the largest for masking images that possessed significant higher order image statistics (scene images and scene textures) as compared with masking images that did not (phase-randomized scenes and white noise), with scene image masks yielding the largest masking effects. In a control study, we eliminated all differences in the second-order statistics of the masks, while maintaining differences in their higher order statistics by comparing masking by scene textures rather than by their phase-randomized versions, and showed that the former produced significantly stronger gist masking. Experiments 2 and 3 were designed to test whether conceptual masking could account for the differences in the strength of the scene texture and phase-randomized masks used in Experiment 1, and revealed that the recognizability of scene texture masks explained just 1% of their masking variance. Together, the results suggest that (1) masks containing the higher order statistical structure of scenes are more effective at masking scene gist processing than are masks lacking such structure, and (2) much of the disruption of scene gist recognition that one might be tempted to attribute to conceptual masking is due to spatial masking.     

Two scenes or not two scenes: The effects of stimulus repetition and view-similarity on scene categorization from brief displays

Previous research suggests that understanding the gist of a scene relies on global structural cues that enable rapid scene categorization. This study used a repetition blindness (RB) paradigm to interrogate the nature of the scene representations used in such rapid categorization. When stimuli are repeated in a rapid serial visual presentation (RSVP) sequence (~10 items/sec), the second occurrence of the repeated item frequently goes unnoticed, a phenomenon that is attributed to a failure to consolidate two conscious episodes (tokens) for a repeatedly activated type. We tested whether RB occurs for different exemplars of the same scene category, which share conceptual and broad structural properties, as well as for identical and mirror-reflected repetitions of the same scene, which additionally share the same local visual details. Across 2 experiments, identical and mirror-image scenes consistently produced a repetition facilitation, rather than RB. There was no convincing evidence of either RB or repetition facilitation for different members of a scene category. These findings indicate that in the first 100–150 ms of processing scenes are represented in terms of local visual features, rather than more abstract category-general features, and that, unlike other kinds of stimuli (words or objects), scenes are not susceptible to token individuation failure.     

Context-sensitive binding by the laminar circuits of V1 and V2: A unified model of perceptual grouping,attention, and orientation contrast

A detailed neural model is presented of how the laminar circuits of visual cortical areas V1 and V2 implement context-sensitive binding processes such as perceptual grouping and attention. The model proposes how specific laminar circuits allow the responses of visual cortical neurons to be determined not only by the stimuli within their classical receptive fields, but also to be strongly influenced by stimuli in the extra-classical surround. This context-sensitive visual processing can greatly enhance the analysis of visual scenes, especially those containing targets that are low contrast, partially occluded, or crowded by distractors. We show how interactions of feedforward, feedback, and horizontal circuitry can implement several types of contextual processing simultaneously, using shared laminar circuits. In particular, we present computer simulations that suggest how top-down attention and preattentive perceptual grouping, two processes that are fundamental for visual binding, can interact, with attentional enhancement selectively propagating along groupings of both real and illusory contours, thereby showing how attention can selectively enhance object representations. These simulations also illustrate how attention may have a stronger facilitatory effect on low contrast than on high contrast stimuli, and how pop-out from orientation contrast may occur. The specific functional roles which the model proposes for the cortical layers allow several testable neurophysiological predictions to be made. The results presented here simulate only the boundary grouping system of adult cortical architecture. However, we also discuss how this model contributes to a larger neural theory of vision that suggests how intracortical and intercortical feedback help to stabilize development and learning within these cortical circuits. Although feedback plays a key role, fast feedforward processing is possible in response to unambiguous information. Model circuits are capable of synchronizing quickly, but context-sensitive persistence of previous events can influence how synchrony develops. Although these results focus on how the interblob cortical processing stream controls boundary grouping and attention, related modelling of the blob cortical processing stream suggests how visible surfaces are formed, and modelling of the motion stream suggests how transient responses to scenic changes can control long-range apparent motion and also attract spatial attention.     

Learned predictiveness speeds visual processing

When humans learn that the presence of a cue predicts the likelihood of an outcome, they can exploit this learned predictiveness, such that formation of subsequent associations between that cue and new outcomes is facilitated. Could such enhanced selection for association arise early enough to facilitate low-level visual processing? In a test of this possibility, adult volunteers first engaged in a value-learning task involving faces that were differentially predictive of monetary wins or losses. Later, in a simple recognition task, these faces were briefly presented for a variable duration and then masked. The critical presentation duration needed to produce criterion-level recognition was measured to index the visual processing speed for each learned face. Critical duration was significantly shorter for stimuli with high learned predictiveness than for stimuli with low learned predictiveness, regardless of whether they were associated with wins or losses. These results show that neural mechanisms involved in predicting future outcomes are able to modulate visual processing efficiency, probably via cortical feedback processes.     

Diagnostic colours contribute to the early stages of scene categorization: Behavioural and neurophysiological evidence

We examined the effects of colour cues on the express categorization of natural scenes. Using a go/no-go paradigm sensitive to fast recognition processes, we measured early event-related potential (ERP) correlates of scene categorization to elucidate the processing stage at which colour contributes to scene recognition. Observers were presented with scenes belonging to four colour-diagnostic categories (desert, forest, canyon and coastline). Scenes were presented in one of three forms: Diagnostically coloured, nondiagnostically coloured, or greyscale images. In a verification task, observers were instructed to respond whenever the presented stimulus matched a previously presented category name. Reaction times and accuracy were optimal when the stimuli were presented as their original diagnostically coloured version, followed by their greyscale version, and lastly by their nondiagostically coloured version. These effects were mirrored in the early (i.e., 150 ms following stimulus onset) ERP frontal correlates. Their onset was delayed for greyscale scenes compared to diagnostically coloured scenes, and for nondiagnostically coloured scenes compared to the other two conditions. Frontal ERP amplitudes also decreased for greyscale and nondiagnostically coloured scenes. Together, the results suggest that diagnostic colours are part of the scene gist responsible for express scene categorization.