Expectancy and visual-spatial attention: Effects on perceptual quality.

Abstract

When we expect important stimuli at a particular spatial location, how does our perceptual sensitivity change over space? Subjects were cued to expect a target stimulus at one location and then required to perform one of the following tasks at that and three other locations: luminance detection, brightness discrimination, orientation discrimination, or form discrimination. The analysis of subjects' performance according to signal detection theory revealed changes in both sensitivity and bias for each of these tasks. Sensitivity was maximally enhanced at the location where a target stimulus was expected and generally decreased with distance from that location. Factors that influenced the gradient of sensitivity were (a) the type of task performed and (b) the spatial distribution of the stimuli. Sensitivity fell off more steeply over distance for orientation and form discrimination than for luminance detection and brightness discrimination. In addition, it fell off more steeply when stimuli were near each other than when they were farther apart.

The role of visual attention in saccadic eye movements

“…This result is consistent with the general finding in other studies that used cost-benefit paradigms to study the allocation of visual attention to different spatial locations (Downing, 1988;Hawkins et aI., 1990;Posner et aI., 1978). In these studies, subjects' performance in a target detection task benefited from advance knowledge of the target location and suffered if the target appeared at an unexpected location.…”

“…A likely candidate is the spatial attention system, a mechanism that can operate within a fixation to selectively process information from different locations (Eriksen & Hoffman, 1973, 1974Hoffman, 1975;Hoffman & Nelson, 1981;Posner, 1980;Posner, Nissen, & Ogden, 1978). Allocating attention to a position in space results in faster and more accurate processing of luminance and form information in a region of space surrounding that location (Bash inski & Bacharach, 1980;Downing, 1988;Hawkins et al, 1990;Hoffman & Nelson, ). In addition to enhancing perceptual processing, attention may also be important in guiding "action systems," such as reaching (Allport, 1987(Allport, , 1991.…”

Linking Attention to Learning, Expectation, Competition, and Consciousness

“…More generally, the prediction that top-down attention has an on-center off-surround characteristic has received a considerable amount of psychological and neurobiological empirical confirmation in the visual system (Bullier, et al, 1996;Caputo and Guerra, 1998;Downing, 1988;Mounts, 2000;Reynolds, Chelazzi, and Desimone, 1999;Smith, Singh, and Greenlee, 2000;Somers, et al, 1999;Sillito, et al, 1994;Steinman, Steinman, and Lehmkuhle, 1995;Vanduffell, Tootell, and Orban, 2000). In particular, the claim that bottom-up sensory activity is enhanced when matched by top-down on-center signals is in accord with an extensive neurophysiological literature showing the facilitatory effect of attentional feedback (Luck, et al, 1997;Roelfsema, et al, 1998;Sillito, et al, 1994), but not with models in which matches with top-down feedback cause suppression (Mumford, 1992;Rao and Ballard, 1999).…”

Variability of response times as a marker of diverted attention

“…of response times covary as a function of the intensity of the stimulus [18]; mean RTs and their S.D.s increase in parallel as stimulus intensity decreases. On the other hand, spatial attention is known to enhance perceptual sensitivity at the attended location [7,12,23]. If this enhancement is interpreted as a subjective increase in stimulus intensity, one can conclude that not only mean RTs, but also their variability should increase at unattended locations.…”