Saccade-contingent change detection provides a powerful tool for investigating scene representation and scene memory. In the present study, critical objects presented within color images of naturalistic scenes were changed during a saccade toward or away from the target. During the saccade, the critical object was changed to another object type, to a visually different token of the same object type, or was deleted from the scene. There were three main results. First, the deletion of a saccade target was special: Detection performance for saccade target deletions was very good, and this level of performance did not decline with the amplitude of the saccade. In contrast, detection of type and token changes at the saccade target, and of all changes including deletions at a location that had just been fixated but was not the saccade target, decreased as the amplitude of the saccade increased. Second, detection performance for type and token changes, both when the changing object was the target of the saccade and when the object had just been fixated but was not the saccade target, was well above chance. Third, mean gaze durations were reliably elevated for those trials in which the change was not overtly detected. The results suggest that the presence of the saccade target plays a special role in transsaccadic integration, and together with other recent findings, suggest more generally that a relatively rich scene representation is retained across saccades and stored in visual memory.

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Our knowledge of the way that the visual system operates in everyday behavior has, until recently, been very limited. This information is critical not only for understanding visual function, but also for understanding the consequences of various kinds of visual impairment, and for the development of interfaces between human and artificial systems. The development of eye trackers that can be mounted on the head now allows monitoring of gaze without restricting the observer's movements. Observations of natural behavior have demonstrated the highly task-specific and directed nature of fixation patterns, and reveal considerable regularity between observers. Eye, head, and hand coordination also reveals much greater flexibility and task-specificity than previously supposed. Experimental examination of the issues raised by observations of natural behavior requires the development of complex virtual environments that can be manipulated by the experimenter at critical points during task performance. Experiments where we monitored gaze in a simulated driving environment demonstrate that visibility of task relevant information depends critically on active search initiated by the observer according to an internally generated schedule, and this schedule depends on learnt regularities in the environment. In another virtual environment where observers copied toy models we showed that regularities in the spatial structure are used by observers to control eye movement targeting. Other experiments in a virtual environment with haptic feedback show that even simple visual properties like size are not continuously available or processed automatically by the visual system, but are dynamically acquired and discarded according to the momentary task demands.

The ability of animals to select a limited region of sensory space for scrutinyisanimportant factor in dealing with cluttered or complex sensory environments. Such an #attentional" system in the visual domain is believed to be involved in both the perception of objects and the control of eyemovements in primates. While wecanintentionally guide our attention to perform a speci#c task, it is also re#exively drawn to #salient" features in our sensory input space. Understanding how high-level task information and low-level stimulus information can combine to control our sensory processing is of great interest to both neuroscience and engineering. Towards this end, wehave designed and fabricated a one-dimensional, analog VLSI vision chip that models covert attentional search and tracking. We extend previous analog VLSI work #Morris and DeWeerth, 1997# on delayed inhibition in a winner-take-all network to use extracted image edges as input to the attentional saliency map and to perform serial search on a particular feature conjunction #spatial derivative and direction-of-motion#. We further demonstrate the abilitytomodifythe circuit's parameters #on-the-#y" to switchbetween a search mode and a tracking mode.

this paper, we will argue that despite these failures of explicit change detection, participant's visual memory representation of the scene was nevertheless sensitive to the difference between views. Specifically, consecutive views of the scene were compared, and although the difference between views was not sufficient to yield explicit change detection, it was sufficient to update memory to reflect the changed viewpoint. Before directly examining whether memory was updated to reflect recent views (Experiment 2), it is important to eliminate two alternative explanations for the poor explicit change detection performance in Experiment 1. First, changes may have been missed because participants simply failed to construct or retain a representation from a previous view (O'Regan, 1992). Second, it could be that a representation of the previous view was retained across the masked interval, but it was immediately overwritten by perceptual processing of the next view, without comparison of the two views (Rensink et al., 1997)

The change blindness phenomenon suggests that visual representations retained across saccades are very limited. In this paper we sought to specify the kind of information that is in fact retained. We investigated targeting performance for saccadic eye movements, since one need for visual representations across eye and body positions may be to guide coordinated movements. We examined saccades in the context of an ongoing sensory motor task in order to make stronger generalizations about natural visual functioning and deployment of attention. Human subjects copied random patterns of coloured blocks on a computer display. Their eye movement pattern was consistent from block to block, including a precise saccade to a previously-placed, neighbouring block during each additional block placement.This natural, consistent eye movement allowed the previously-placed, neighbouring block to serve as an implicit target without instructions to the subject. On random trials, we removed the target object from the display during a preceding saccade, so that observers were required to make the targeting saccade without a currently visible target. Targeting performance was excellent, and appeared to be influenced by spatial information that was not visible during the preceding fixation. Subjects were generally unaware of the disappearance and reappearance of the target. We conclude that spatial information about visual targets is retained across eye movements and used to guide subsequent movements.

This paper reviews research examining the role of visual memory in scene perception and visual search. Recent theories in these literatures have held that coherent object representations in visual memory are fleeting, disintegrating upon the withdrawal of attention from an object. I discuss evidence demonstrating that, far from being transient, visual memory supports the accumulation of information from scores of individual objects in scenes, utilizing both visual short-term memory and visual long-term memory. In addition, I review evidence that memory for the spatial layout of a scene and memory for specific object positions can efficiently guide search within natural scenes. In the past decade, the interaction between perception and memory has received a great deal of attention from cognitive scientists. Much of this interest has originated from increased understanding that perception is a dynamic, serial process, extended over space and time. In this paper, I will discuss two related lines of research in which the relationship between perception and memory has come to the fore: Scene perception and visual

Attention and working memory limitations set strict limits on visual representations, yet researchers have little appreciation of how these limits constrain the acquisition of information in ongoing visually guided behavior. Subjects performed a brick sorting task in a virtual environment. A change was made to 1 of the features of the brick being held on about 10 % of trials. Rates of change detection for feature changes were generally low and depended on the pick-up and put-down relevance of the feature to the sorting task. Subjects ’ sorting decision suggests that changes may be missed because of a failure to update the changed feature. The authors also explore how hand and eye behavior are coordinated for strategic acquisition and storage of visual information throughout the task.

or their technical expertise. Correspondence concerning this article should be addressed to John M. Henderson, Department of Psychology, Michigan State University, East Lansing, Michigan, 48824-1117. Electronic mail may be sent to john@eyelab.msu.edu. bject perception is a dynamic process: The entire visual scene disappears and then reappears three to four times each second during saccadic eye movements. How does the human visual system integrate this continually changing input? The purpose of the present study was to investigate the nature of the representational systems that support the retention and integration of information about real-world objects across saccades during dynamic visual perception. One intuitively appealing hypothesis concerning transsaccadic integration is that detailed sensory representations are created and fused from one fixation to the next within a spatiotopically organized reference frame (e.g., Breitmeyer, 1984; Davidson, Fox, & Dick, 1973;

Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this change blindness can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, and to cast new light on the way that it is — and is not — involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of seeing. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a �irtual representation, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This sensing is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself — the mechanisms involved when scrutinizing items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved. © 2000