Academic journal article Attention, Perception and Psychophysics

Limited Influence of Perceptual Organization on the Precision of Attentional Control

Academic journal article Attention, Perception and Psychophysics

Limited Influence of Perceptual Organization on the Precision of Attentional Control

Article excerpt

The role of perceptual organization in the precision of attentional control was assessed in three experiments. Observers viewed circular arrays of disks that varied in density. One disk was cued, directing attention to that disk. A series of tones then indicated shifts of attention to the next disk that was of the same color (Experiments 1 and 2) or on the same depth plane (Experiment 3). In the homogeneous condition, all of the disks were the same color (Experiments 1 and 2) or on the same depth plane (Experiment 3). In the heterogeneous condition, the disks alternated in color (Experiments 1 and 2) or stereoscopically defined depth (Experiment 3). If the observers were able to limit attention to disks within a group, the effective density of the displays in the heterogeneous conditions should have been one half that in the homogeneous conditions. There was little evidence that the observers could do this, indicating a limited role of perceptual organization in the precision of attentional control.

Researchers have made use of a variety of metaphors to guide discussion of the mechanisms underlying visual attention (for reviews, see Cave & Bichot, 1999; Fernandez- Duque & Johnson, 1999). Perhaps the most prevalent is that attention is a spotlight into which some information falls and other information does not (e.g., Posner, 1980; Posner, Snyder, & Davidson, 1980; cf. Cave & Bichot, 1999). Metaphors other than the attentional spotlight, however, have been used frequently as well. These include attention as a zoom lens (e.g., Eriksen & St. James, 1986; Eriksen & Yeh, 1985), attention as a gradient filter (e.g., LaBerge & Brown, 1989), and attention as a nonlinear filter (e.g., Cutzu & Tsotsos, 2003; Tsotsos et al., 1995). Common to all of these metaphors is the characterization that some information in the retinal image is processed differently than other information and that there is an active selection process that is controlled, at least in part, by the observer. Questions arise then concerning what factors determine what information is selected and what the limitations of the selection process are.

The present article is concerned with limitations of the spatial extent of the selection process and, in particular, the extent to which the organization of a visual scene can influence the spatial extent of selection. The spatial extent of attention has been investigated using a variety of methods. For example, the flankers task (e.g., Eriksen & Hoffman, 1972) requires observers to report the identity of a stimulus at one location (the target) while ignoring the identity of nearby stimuli (the flankers). If the flankers are too close to the target, observers' responses tend to be systematically influenced by the identity of the flankers. This is taken as evidence that the spatial extent of attention cannot be reduced to the size of that separation. Using this method, Eriksen and Hoffman estimated the minimal spatial extent of selection to be about 1? of visual angle; flankers that were separated from the target by more than that had no influence on responses to the target. Other researchers, using spatial cuing combined with probe detection and related methods, proposed a gradient area of selection extending as much as 19? from a cued location (e.g., Downing & Pinker, 1985; Henderson & Macquistan, 1993; LaBerge & Brown, 1986). Still others, using methods involving many distractors and, sometimes, multiple targets separated by variable distances, have suggested that the area of selection has a facilitatory-center-inhibitory-surround profile with a spatial extent that is as large as 6? and as small as 1? (e.g., Bahcall & Kowler, 1999; Cutzu & Tsotsos, 2003; Mounts, 2000a, 2000b; Steinman, Steinman, & Lehmkuhle, 1995). Finally, some researchers have suggested that the spatial extent and shape of attentional selection varies with the task and with the properties of the stimuli (e. …

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