Impossible shadows and the shadow correspondence problem

Shadows cast by objects contain potentially useful information about the location of these objects in the scene as well as their surface reflectance. However, before the visual system can use this information, it has to solve the shadow correspondence problem, that is to match the objects with their respective shadows. In the first experiment, it is shown that the estimate of the light source position is affected by a gradual luminance ramp added to the image. In the second experiment, it is shown that observers process impossible shadow images as if they ignored the local features of the objects. All together, the results suggest that the visual system solves the shadow correspondence problem by relying on a coarse representation of the scene.     

物体相似性对空间表征的影响：来自眼动的证据

以三维场景图片为实验材料,采用眼动追踪技术,通过两个实验考察了对称场景中物体相似性对空间表征的影响。结果表明：（1）无相似物体条件下,场景本身的内在结构对空间表征有重要影响,对称轴方向可以作为空间表征参照方向;（2）存在部分相似物体条件下,物体的相似性会影响空间表征参照方向的选择,并且相似物体方向也是空间表征的参照方向之一。     

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.     

虚拟场景中不同客体朝向条件对内在参照系建立的影响

通过眼动记录和部分场景再认两种方法,探讨了虚拟建筑物对称场景中物体朝向统一、凸显两种条件对内在参照系建立的影响。结果发现:(1)场景中均为有朝向建筑物且朝向统一时,被试选择物体朝向与对称轴建立内在参照系的可能性没有差异;(2)场景中只有一个有朝向建筑物,其余均为无朝向物体时,即朝向凸显条件下,被试倾向于选择对称轴来建立内在参照系。物体朝向对内在参照系建立的影响作用具有局限性和不稳定性。     

A computational framework for attentional object discovery in RGB-D videos

We present a computational framework for attention-guided visual scene exploration in sequences of RGB-D data. For this, we propose a visual object candidate generation method to produce object hypotheses about the objects in the scene. An attention system is used to prioritise the processing of visual information by (1) localising candidate objects, and (2) integrating an inhibition of return (IOR) mechanism grounded in spatial coordinates. This spatial IOR mechanism naturally copes with camera motions and inhibits objects that have already been the target of attention. Our approach provides object candidates which can be processed by higher cognitive modules such as object recognition. Since objects are basic elements for many higher level tasks, our architecture can be used as a first layer in any cognitive system that aims at interpreting a stream of images. We show in the evaluation how our framework finds most of the objects in challenging real-world scenes.     

多视点学习条件下空间表征的朝向特异性

让被试在没有外界参照线索的条件下,从三个观察视点学习物体场景,首次以局部场景再认范式探讨了空间记忆中场景表征的朝向特异性。结果表明：（1）多视点学习条件下,场景空间表征依然是依赖于特定朝向的,不支持空间表征独立于朝向和空间表征依赖于多个观察朝向的观点。（2）场景空间表征的朝向依赖性不仅表现于方位判断任务,也同样表现于场景再认任务。（3）场景本身的内在结构对空间表征中参照系的选取有重要影响。     

Iconic memory for natural scenes: Evidence using a modified change-detection procedure

ABSTRACT

Change blindness for the contents of natural scenes suggests that only items that are attended while the scene is still visible are stored, leading some to characterize our visual experiences as sparse. Experiments on iconic memory for arrays of discrete symbols or objects, however, indicate observers have access to more visual information for at least several hundred milliseconds at offset of a display. In the experiment presented here, we demonstrate an iconic memory for complex natural or real-world scenes. Using a modified change detection task in which to-be changed objects are cued at offset of the scene, we show that more information from a natural scene is briefly stored than change blindness predicts and more than is contained in visual short-term memory. In our experiment, a cue appearing 0, 300, or 1000?msec after offset of the pre-change scene or at onset of the second scene presentation (a Post Cue) directed attention to the location of a possible change. Compared to a no-cue condition, subjects were significantly better at detecting changes and identifying what changed in the cue condition, with the cue having a diminishing effect as a function of time and no effect when its onset coincided with that of the second scene presentation. The results suggest that an iconic memory of a natural scene exists for at least 1000?msec after scene offset, from which subjects can access the identity of items in the pre-change scene. This implies that change blindness underestimates the amount of information available to the visual system from a brief glance of a natural scene.     

Spatial reference in multiple object tracking

Spatial reference in multiple object tracking is available from configurations of dynamic objects and static reference objects. In three experiments, we studied the use of spatial reference in tracking and in relocating targets after abrupt scene rotations. Observers tracked 1, 2, 3, 4, and 6 targets in 3D scenes, in which white balls moved on a square floor plane. The floor plane was either visible thus providing static spatial reference or it was invisible. Without scene rotations, the configuration of dynamic objects provided sufficient spatial reference and static spatial reference was not advantageous. In contrast, with abrupt scene rotations of 20°, static spatial reference supported in relocating targets. A wireframe floor plane lacking local visual detail was as effective as a checkerboard. Individually colored geometric forms as static reference objects provided no additional benefit either, even if targets were centered on these forms at the abrupt scene rotation. Individualizing the dynamic objects themselves by color for a brief interval around the abrupt scene rotation, however, did improve performance. We conclude that attentional tracking of moving targets proceeds within dynamic configurations but detached from static local background.     

Continuous visual cues trigger automatic spatial target updating in dynamic scenes

Dynamic tasks often require fast adaptations to new viewpoints. It has been shown that automatic spatial updating is triggered by proprioceptive motion cues. Here, we demonstrate that purely visual cues are sufficient to trigger automatic updating. In five experiments, we examined spatial updating in a dynamic attention task in which participants had to track three objects across scene rotations that occurred while the objects were temporarily invisible. The objects moved on a floor plane acting as a reference frame and unpredictably either were relocated when reference frame rotations occurred or remained in place. Although participants were aware of this dissociation they were unable to ignore continuous visual cues about scene rotations (Experiments 1a and 1b). This even held when common rotations of floor plane and objects were less likely than a dissociated rotation (Experiments 2a and 2b). However, identifying only the spatial reference direction was not sufficient to trigger updating (Experiment 3). Thus we conclude that automatic spatial target updating occurs with pure visual information.     

Effects of verbal and nonverbal interference on spatial and object visual working memory

We tested the hypothesis that a verbal coding mechanism is necessarily engaged by object, but not spatial, visual working memory tasks. We employed a dual-task procedure that paired n-back working memory tasks with domain-specific distractor trials inserted into each interstimulus interval of the n-back tasks. In two experiments, object n-back performance demonstrated greater sensitivity to verbal distraction, whereas spatial n-back performance demonstrated greater sensitivity to motion distraction. Visual object and spatial working memory may differ fundamentally in that the mnemonic representation of featural characteristics of objects incorporates a verbal (perhaps semantic) code, whereas the mnemonic representation of the location of objects does not. Thus, the processes supporting working memory for these two types of information may differ in more ways than those dictated by the "what/where" organization of the visual system, a fact more easily reconciled with a component process than a memory systems account of working memory function.     

Redundant spoken labels facilitate perception of multiple items

Because of the strong associations between verbal labels and the visual objects that they denote, hearing a word may quickly guide the deployment of visual attention to the named objects. We report six experiments in which we investigated the effect of hearing redundant (noninformative) object labels on the visual processing of multiple objects from the named category. Even though the word cues did not provide additional information to the participants, hearing a label resulted in faster detection of attention probes appearing near the objects denoted by the label. For example, hearing the word chair resulted in more effective visual processing of all of the chairs in a scene relative to trials in which the participants attended to the chairs without actually hearing the label. This facilitation was mediated by stimulus typicality. Transformations of the stimuli that disrupted their association with the label while preserving the low-level visual features eliminated the facilitative effect of the labels. In the final experiment, we show that hearing a label improves the accuracy of locating multiple items matching the label, even when eye movements are restricted. We posit that verbal labels dynamically modulate visual processing via top-down feedback--an instance of linguistic labels greasing the wheels of perception.