Parallel versus serial processing in rapid pattern discrimination

Abstract

When stimuli are available for just a brief period (approximately 100 ms) only restricted spatial information can be processed by the visual system. If the stimuli are presented very briefly, eye movements are not possible. The time during which the after-image of the stimulus is available for inspection is terminated by presentation of a masking pattern. We show here that in these conditions a small pattern is easily detected against a background made up of many others, only if this target pattern differs from the background patterns in certain local features. In this case the detectability of the target is almost independent of the number of background elements, suggesting that a parallel process is operating. Detection of patterns not differing from their backgrounds in such features requires focal attention which is a serial process. The aperture of this attention is scaled to minimize the number of shifts of attention required.

Conjunction search revisited.

“…(a) They replicated the finding by Bergen and Julesz (1983) that search for a T among Ls (in four different orientations) is serial, and confirmed that this was the case even for subjects who showed parallel search with conjunctions of color, size, and shape. This is consistent with the claim that parallel search depends on control from separate feature maps.…”

Contextual Masking of Oriented Lines: Interactions Between Surface Segmentation Cues

“…Differential orientation of texture elements (see Fig. 1) is a potent cue for perceptual segmentation (Bergen and Julesz 1983;Caputo 1996;Foster and Westland 1995;Li et al 2000) and has a marked influence over orientation judgments (Mareschal et al 2001;Sekuler 1965;Wehrhahn et al 1996;Westheimer et al 1976). Similarly, responses to oriented CRF stimuli have been found to be stronger in the presence of textured surrounds that promote perceptual segmentation (orthogonal lines) than in the presence of surrounds that do not promote segmentation (parallel lines) (Cavanaugh et al 2002;Fries et al 1977;Gilbert and Wiesel 1990;Knierim and van Essen 1992;Lamme 1995;Levitt and Lund 1997;Li et al 2000;Nelson and Frost 1978;Zipser et al 1996).…”

“…Image features that are physically distinct from their surroundings are more easily detected than those that are not (e.g., Beck 1972;Bergen and Julesz 1983;Treisman and Gelade 1980). Abundant evidence also exists to conclude that specific attributes of image features distinguished in this manner are also more easily discriminable than are attributes of features that blend into their surroundings (e.g., Caputo 1996;Mareschal et al 2001;Wehrhahn et al 1996).…”

Pop-out from abrupt visual onsets

“…Such elements are therefore said to 'pop-out' (Nothdurft 1991). Rapid detection within a large array of surrounding elements is evidence that this figure-ground segregation occurs preattentively (Bergen & Julesz, 1983;Nothdurft, 1992). As pop-out effects are strong and well established we designed our experiments to ask whether they apply specifically to the perception of a set of abrupt onsets containing one element that contrasts with all the other new elements.…”