Human object recognition is generally considered to tolerate changes of the stimulus position in the visual field. A number of recent studies, however, have cast doubt on the completeness of translation invariance. In a new series of experiments we tried to investigate whether positional specificity of short-term memory is a general property of visual perception. We tested same-different discrimination of computer graphics models that were displayed at the same or at different locations of the visual field, and found complete translation invariance, regardless of the similarity of the animals and irrespective of direction and size of the displacement (Exp. 1 and 2). Decisions were strongly biased towards same decisions if stimuli appeared at a constant location, while after translation subjects displayed a tendency towards different decisions. Even if the spatial order of animal limbs was randomized ("scrambled animals"), no deteriorating effect of shifts in the field of view could be ...

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

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

Intuitively, dynamic visual stimuli, such as moving objects or flashing lights, attract attention. Visual search tasks have revealed that dynamic targets among static distractors can indeed efficiently guide attention. The present study shows that the reverse case, a static target among dynamic distractors, allows for relatively efficient selection in certain but not all cases. A static target was relatively efficiently found among distractors that featured apparent motion, corroborating earlier findings. The important new finding was that static targets were equally easily found among distractors that blinked on and off continuously, even when each individual item blinked at a random rate. However, search for a static target was less efficient when distractors abruptly varied in luminance but did not completely disappear. The authors suggest that the division into the parvocellular pathway dealing with static visual information, on the one hand, and the magnocellular pathway common to motion and new object onset detection, on the other hand, allows for efficient filtering of dynamic and static information.

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Visual short-term memory (VSTM) has received intensive study over the past decade, with research focused on VSTM capacity and representational format. Yet, the function of VSTM in human cognition is not well understood. Here, the authors demonstrate that VSTM plays an important role in the control of saccadic eye movements. Intelligent human behavior depends on directing the eyes to goal-relevant objects in the world, yet saccades are very often inaccurate and require correction. The authors hypothesized that VSTM is used to remember the features of the current saccade target so that it can be rapidly reacquired after an errant saccade, a task faced by the visual system thousands of times each day. In 4 experiments, memory-based gaze correction was accurate, fast, automatic, and largely unconscious. In addition, a concurrent VSTM load interfered with memory-based gaze correction, but a verbal short-term memory load did not. These findings demonstrate that VSTM plays a direct role in a fundamentally important aspect of visually guided behavior, and they suggest the existence of previously unknown links between VSTM representations and the occulomotor system.

Four experiments examined episodic recognition memory for series of brieflypresented, synthetic human faces. In each experiment, a series of study faces was followed by a probe face, which the subject judged as having been present in the study series or not. The experiments revealed that the similarity stucture of synthetic faces strongly influenced recognition memory, but that recognition was not much influenced by information about the category from which particular faces came. Comparing results against predictions from a model in which information was retained in memory with no loss, confirmed that increasing length of study lists directly a#ected memory.

When two dot arrays are briefly presented, separated by a short interval of time, visual short-term memory of the first array is disrupted if the interval between arrays is shorter than 300-500 ms (Brockmole, Wang, & Irwin, 2002). Here we investigated whether such a time window was triggered by the necessity to integrate arrays. Using a probe task we removed the need for integration but retained the requirement to represent the images. We found that a long time window was needed for performance to reach asymptote even when integration across images was not required. Furthermore, such window was lengthened if subjects had to remember the locations of the second array, but not if they only conducted a visual search among it. We suggest that a temporal window is required for consolidation of the first array, which is vulnerable to disruption by subsequent images that also need to be memorized.

Two dot arrays, each containing a different set of 6 randomly selected locations from a 5x5 matrix, were presented briefly and separated by an inter-stimulusinterval (ISI) of 0, 200, 500, or 1500ms. Subjects were asked to remember these locations and to report whether a probe dot matched the memory locations. To find out whether subjects formed an integrated representation of the two arrays, the probe dot was accompanied by matrix elements from the first array, from the second array, or from both arrays. Memory for array 1 was significantly impaired when the retrieval context was drawn from array 2, and vice versa, suggesting that the two arrays were represented separately. This effect was observed only at an ISI of 500ms or longer. We propose that as array 1 is better consolidated, it representation becomes more separated from that of array 2. 2 An important challenge confronting the human visual system during natural viewing is to extract complex visual information and to retain it momentarily. A lot of vision research has focused on how the visual system perceives objects and scenes (Palmer, 1999), and how such information is retained in visual short-term memory (Intraub, 1997; Jiang, Olson, & Chun, 2000; Luck & Vogel, 1997; Phillips, 1974; Rensink, O'Regan, & Clark, 1997; Wheeler & Treisman, 2002). Recent studies suggest that approximately four visual objects or six spatial locations can be stored in VSTM simultaneously (Luck & Vogel, 1997; Pashler, 1988). More features can be stored in VSTM if they conjoin to form integrated objects than if they are separate (Lee & Chun, 2001; Luck & Vogel, 1997; Olson & Jiang, 2002; Xu, 2002; Wheeler & Treisman, 2001). These studies have focused on the representation of a single visual display in VSTM. However, visual events evolv...

Visual episodic recognition memory was assessed in young (mean age 22.5 years) and older (mean age 74.1 years) adults. To isolate purely visual memory, recognition was tested with sets of briefly-presented compound sinusoidal gratings, which minimized age-related differences in visual processing, and resisted verbal encoding. Recognition was measured after delays of 1, 2 or 4 seconds. Overall, neither accuracy of recognition nor speed of response differed significantly between groups, or with probe delay, which strengthens recent claims that visual memory tends to be spared during the course of normal aging. Studies with rehearsable verbal stimuli such as letters, words or sentences suggest that normal adult aging is associated with diminished short-term memory (e.g., Kausler, 1994; Wingfield & Stine-Morrow, 2000; Wingfield & Kahana, 2002). However, recent research raises questions about whether this association extends to memory for other kinds of test materials. For example, using a match-to-sample procedure, McIntosh et al. (1999) found that younger and older observers had virtually identical short-term memory for a single, briefly-presented, vertical sinusoidal grating. Functional neuroimaging studies of the participants ’ brains, led McIntosh et al. to speculate that a compensatory reorganization of neural circuits helped to preserve visual memory in older participants. Subsequently, with a slightly modified test procedure, Bennett, Sekuler, McIntosh, and Della-Maggiore (2001) confirmed the absence of age-related differences in short-term memory for sinusoidal gratings. Such stimuli can be valuable probes of memory because their representations in early vision are known and, because they resist naming or other symbolic encoding, they promote reliance on a form of short-term memory that uses purely visual information