Vision outside the focus of attention

Braun, Jochen; Sagi, Dov

doi:10.3758/bf03205010

Cited by 195 publications

(144 citation statements)

References 57 publications

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“…This asymmetry may result from local detection being performed in an earlier cortical level (V1) and being less subject to high-level attentional control. The asymmetry also agrees with previous findings indicating that, of these early vision tasks, orientation identification requires attentional resources (26,27), while local detection is performed automatically (19,28). This distinction is supported by our own anecdotal observation that subjects performing global identification sometimes spontaneously reported that the odd element "popped-out," while no subject performing local detection remembered noticing variation of the array orientation.…”

Section: Discussionsupporting

confidence: 81%

Attentional control of early perceptual learning.

Ahissar

Hochstein

1993

Proc. Natl. Acad. Sci. U.S.A.

439

374

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The performance of adult humans in simple vsual tasks improves dramatically with practice. This improvement is highly speciffc to basic attributes of the trained stimulus, suggesting that the underlying changes occur at low-level processing stages in the brain, where different orientations and spatial frequencies are handled by separate channels. We asked whether these practice effects are determined solely by activity in stimulus-driven mechanisms or whether high-level attentional mechanisms, which are linked to the perceptual task, might control the learning process. We found that practicing one task did not improve performance in an alternative task, even though both tasks used exactly the same visual stimuli but depended on different stimulus attributes (either orientation of local elements or global shape). Moreover, even when the experiment was designed so that the same responses were associated with the same stimuli (although subjects were instructed to attend to the attribute underlying one task), learning did not transfer from one task to the other. These results suggest that specific high-level attentional mechanisms, controlling changes at early visual processing levels, are essential in perceptual learning.Recent psychophysical studies have found that perceptual learning (in various visual tasks) is specific to stimulus attributes. Improvement in performance does not transfer to different spatial locations (1-4, 35), orientations (4-6, 35), spatial frequencies (5), or even, in some cases, across eyes (refs. 4 and 7 and somewhat in ref. 8). This has implications about the site(s) of perceptual learning. There is both anatomical and physiological evidence for hierarchical information processing in the visual system. Neurons at lower levels ofthe visual pathway are highly specialized for position, size, orientation, spatial frequency, and eye of origin. Neurons in higher anatomical visual areas (9), however, generalize over these stimulus variables (see ref. 10 and 11 for reviews) and are sensitive to increasingly more complex aspects of the stimuli. These considerations imply that stimulus-specific learning-induced changes occur at an early cortical processing stage, perhaps in primary visual cortex.However, previous studies of perceptual learning did not test the possibility that there might be both stimulus specificity as well as specificity to the behavioral context of the training. Computational considerations suggest that solving many complex image processing tasks in vision may involve an initial "bottom-up" processing stage (i.e., determined only by retinal input) followed by analysis at later stages, which are top-down modulated (i.e., controlled by extraretinal input such as prior knowledge about the task; refs. 12 and 13). This notion agrees with findings from behaving monkeys where the firing rates of neurons in higher visual areas are more strongly modulated by top-down task-dependent influences than neurons in early cortical areas (refs. 14-17; for a review, see ref. 18). According...

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Section: Discussionsupporting

confidence: 81%

Attentional control of early perceptual learning.

Ahissar

Hochstein

1993

Proc. Natl. Acad. Sci. U.S.A.

439

374

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“…Or does grouping occur even when attentive resources are unavailable (e.g., because they are committed elsewhere)? In earlier work on texture segregation, we found that this perceptual process is largely independent of the availability of the resources of visual attention (Braun & Sagi, 1990, and this result is once more confirmed here. Given the apparent similarity between perceptual grouping and texture segregation (Beck, 1982;Treisman, 1982), we wanted to investigate whether perceptual grouping is as independent of attentive resources as texture segregation appears to be.…”

supporting

confidence: 75%

“…In previous work, we found that the detection or localization of a textural singularity is carried out normally even when visual attention is focused at a distant location in the field of view (the location of the target of a concurrent form identification task), suggesting that at least some tasks based on segregative mechanisms pose little or no demand for attentive resources (Braun & Sagi, 1990. More generally, we suspect that local perceptual salience within homogeneous and dense stimulus textures is attenuated by resource-inexpensive (or -free) processes everywhere except in the immediate vicinity of texture borders, thus permitting the resource-inexpensive (or -free) detection and localization of textural borders and singularities (Rubenstein & Sagi, 1990;Sagi, 1991).…”

mentioning

confidence: 99%

Visual attention and perceptual grouping

Ben-Av

Sagi

Braun

1992

Perception & Psychophysics

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109

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Perceptual organization is thought to involve an analysis of both textural discontinuities and perceptual grouping. In earlier work, we found that textural discontinuities were detected normally even when visual attention was engaged elsewhere. Here we report how perceptual grouping is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of similarity. Four tasks were investigated, some requiring the observer to discriminate between horizontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identification task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of grouping performance in each case. No performance reduction was observed when either form identification or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual attention, whereas the detection of a textural discontinuity does not.

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“…To resolve this paradox, it has even been suggested that our experience of a rich visual world in front of our eyes is a 'grand illusion' sustained by memory [20]. On a less grand but still helpful scale, visual capacity was found to be more commodious than at first apparent, thanks to bottom-up interactions mediating conscious access 'outside the focus' of attention [11][12][13][14]. For about the same time, we have known that observers process natural scenes extremely rapidly, at least to the point of recognising 'gist' [2][3][4].…”

Section: Resultsmentioning

confidence: 99%

“…Trained psychophysical observers are aware of salient stimuli 'outside the focus' of attention and discriminate some of their attributes (e.g., contrast, colour, orientation, …), although more complex attributes remain indistinguishable (e.g., rotated Ts and Ls, colouring of two-coloured disks) [11,12]. Prior familiarity with flashed, masked display turns out to be important to these findings [13,14].…”

Section: Vision Without Attentionmentioning

confidence: 99%

Natural scenes upset the visual applecart

Braun¹

2003

Trends in Cognitive Sciences

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The effortless ease of everyday vision seems to conflict with laboratory findings on the limited capacity of visual attention. It now appears that naturalistic stimuli escape the stringent limitations of attention that apply to seemingly far simpler stimuli. This astonishing result will oblige us to rethink the nature of visual attention and its limited capacity.Everyday vision differs in many ways from what is commonly studied in vision laboratories. For one, the complex natural scenes that inundate everyday vision are far cry from the meagre fare of geometric primitives (letters, gratings, etc.) served in most laboratories. For another, the stimuli of everyday vision are rarely as repetitious as those used in the laboratory, raising the spectre of narrow skills more highly practised than their everyday counterparts. The list of differences lengthens further when we consider dynamic aspects of vision, integration with eye movements, and so forth. These are sobering thoughts for anyone hoping to understand vision in the real world, for it means that laboratory findings will not necessarily generalise to the domain of ultimate interest.Li, Van Rullen, and colleagues [1] now report a particularly dramatic failure to generalise from simple to naturalistic stimuli. Their key finding is that observers categorise the gist of natural scenes (e.g., does it contain an animal/vehicle?) even though they cannot, under otherwise identical conditions, distinguish simple geometric shapes. Thus it would appear that natural scenes are processed more efficiently, and with less call on attentional resources, than simple geometric shapes. Before accepting this startling conclusion, one will wish to take a closer look at the details. Li and colleagues flash natural scenes briefly in the visual periphery, followed by a custom-made stochastic mask to limit visual persistence. The effective presentation time (= 80ms) falls in the 'ultra-rapid categorisation' range described by . With full attention, observers categorise approximately 3 out of 4 of scenes correctly, that is to say, they correctly distinguish scenes with and without animals/vehicles in about 75% of all trials (Fig. 1A). The same level of performance is obtained for discriminating the simple geometric shapes that serve as a comparison (rotated Ts or Ls, two-coloured disks, Fig. 1BC), although presentation times need to be longer, hinting that this may not be so 'simple' after all. Superiority of natural scenesA yawning gulf separates natural scenes and geometric shapes, however, when the observer's attention is coaxed away from either. For natural images continue to be categorised with the same success rate even in the 'near absence' of attention, whereas

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Vision outside the focus of attention

Cited by 195 publications

References 57 publications

Attentional control of early perceptual learning.

Attentional control of early perceptual learning.

Visual attention and perceptual grouping

Natural scenes upset the visual applecart

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