Grouping with and without attention

Chan, Wai Yen; Chua, Fook K.

doi:10.3758/bf03196554

Cited by 13 publications

(9 citation statements)

References 9 publications

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“…Behavioral studies reported that grouping could influence visual performance even when observers are unaware of the presence of such grouping (26,28). Consistent with these observations, in our study, many of the observers reported after the experiment that they were unaware of the different kinds of groupings present among the shapes and that they simply ignored the background bars during the change-detection task.…”

Section: Methodssupporting

confidence: 79%

Visual grouping in human parietal cortex

Chun

2007

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

156

124

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To efficiently extract visual information from complex visual scenes to guide behavior and thought, visual input needs to be organized into discrete units that can be selectively attended and processed. One important such selection unit is visual objects. A crucial factor determining object-based selection is the grouping between visual elements. Although human lesion data have pointed to the importance of the parietal cortex in object-based representations, our understanding of these parietal mechanisms in normal human observers remains largely incomplete. Here we show that grouped shapes elicited lower functional MRI (fMRI) responses than ungrouped shapes in inferior intraparietal sulcus (IPS) even when grouping was task-irrelevant. This relative ease of representing grouped shapes allowed more shape information to be passed onto later stages of visual processing, such as information storage in superior IPS, and may explain why grouped visual elements are easier to perceive than ungrouped ones after parietal brain lesions. These results are discussed within a neural object file framework, which argues for distinctive neural mechanisms supporting object individuation and identification in visual perception.brain imaging ͉ object processing ͉ visual attention ͉ working memory ͉ fMRI T o comprehend the continuous influx of visual information in everyday life, visual input needs to be organized into discrete units that can be selectively attended and processed. One important selection unit is visual objects, whose formation has been shown to profoundly impact subsequent visual processing (1). An important factor determining object-based selection is the grouping between visual elements by various gestalt principles (2, 3), such as connectedness and closure (4-7). Such grouping cues shape conscious visual perception. For example, after unilateral parietal lesions, observers' ability to perceive the presence of two objects, one on each side of the space, was greatly improved by connecting the two objects with a bar forming one big object with two parts instead of two separated objects (8-10). Likewise, after bilateral parietal lesions that result in Balint's syndrome (11), patients could still perceive a single complex object, but their ability to perceive the presence of multiple visual objects is severely impaired (11-13). Such lesion data point to the importance of the parietal cortex in object-based representations, but our understanding of these parietal object grouping and selection mechanisms in normal observers remains largely incomplete. Parietal brain responses have been associated with the number of visual objects actively represented in the mind, including those from the inferior intraparietal sulcus (IPS), which participates in attention-related processing (14-16), and the superior IPS, whose response correlates with the number of objects successfully stored in visual short-term memory (VSTM) (17-20, †). For example, when observers retain variable numbers of object shapes in VSTM, inferior IPS functiona...

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Section: Methodssupporting

confidence: 79%

Visual grouping in human parietal cortex

Chun

2007

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

156

124

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“…Using this method, Moore and Egeth provided evidence that grouping occurs without attention and suggested that grouping failures reported in earlier studies may be due to failures of memory. Subsequent studies supported these findings (Chan & Chua, 2003; Russell & Driver, 2005; Lamy et al, 2006; Shomstein et al, 2010). …”

Section: Introductionmentioning

confidence: 73%

Attention modulates spatio-temporal grouping

2011

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Dynamic stimuli are ubiquitous in natural viewing conditions implying that grouping operations need to operate, not only in space, but also jointly in space and time. Moreover, in natural viewing, attention plays an important role in controlling how resources are allocated. We investigated how attention interacts with spatiotemporal perceptual grouping by using a bistable stimulus, called the Ternus-Pikler display. Ternus-Pikler displays can give rise to two different motion percepts, called Element Motion (EM) and Group Motion (GM), the former dominating at short Inter-Stimulus Intervals (ISIs) and the latter at long ISIs. Our results indicate that GM grouping requires more attentional resources than EM grouping. Different theoretical accounts of perceptual grouping and attention are discussed and evaluated in the light of the current results.

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“…On some of the trials, the black dots were configured to induce a line length illusion in the case of grouping. Remarkably, the dots influenced the line length judgments, even though subjects could not report about the groupings when asked (see also Chan & Chua, 2003). Studies by Kimchi and Razpurker-Apfeld (2004) and Russell and Driver (2005) extended these findings.…”

Section: Previous Experiments On Perceptual Groupingmentioning

confidence: 99%

Incremental grouping of image elements in vision

Roelfsema

Houtkamp

2011

Atten Percept Psychophys

106

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One important task for the visual system is to group image elements that belong to an object and to segregate them from other objects and the background. We here present an incremental grouping theory (IGT) that addresses the role of object-based attention in perceptual grouping at a psychological level and, at the same time, outlines the mechanisms for grouping at the neurophysiological level. The IGT proposes that there are two processes for perceptual grouping. The first process is base grouping and relies on neurons that are tuned to feature conjunctions. Base grouping is fast and occurs in parallel across the visual scene, but not all possible feature conjunctions can be coded as base groupings. If there are no neurons tuned to the relevant feature conjunctions, a second process called incremental grouping comes into play. Incremental grouping is a time-consuming and capacity-limited process that requires the gradual spread of enhanced neuronal activity across the representation of an object in the visual cortex. The spread of enhanced neuronal activity corresponds to the labeling of image elements with object-based attention.

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Grouping with and without attention

Cited by 13 publications

References 9 publications

Visual grouping in human parietal cortex

Visual grouping in human parietal cortex

Attention modulates spatio-temporal grouping

Incremental grouping of image elements in vision

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