Preemption effects in visual search: Evidence for low-level grouping.

Abstract

Experiments are presented showing that visual search for Mueller-Lyer (ML) stimuli is based on complete configurations, rather than component segments. Segments easily detected in isolation were difficult to detect when embedded in a configuration, indicating preemption by low-level groups. This preemption-which caused stimulus components to become inaccessible to rapid search-was an all-ornothing effect, and so could serve as a powerful test of grouping. It is shown that these effects are unlikely to be due to blurring by simple spatial filters at early visual levels. It is proposed instead that they are due to more sophisticated processes that rapidly bind contour fragments into spatially-extended assemblies. These results support the view that rapid visual search cannot access the primitives formed at the earliest stages of visual processing; rather, it can access only higher-level, more ecologically-relevant structures.

The PIG in sPrInG: Evidence on letter grouping from the reading of buried words

“…If there was grouping between the letters of the same case and size across the strings, it might be more difficult to read buried words in singlecase strings (e.g., spring) than in strings with mixed-case letters (e.g., SpRiNg), since grouping between the buried word and the other letters would be stronger in the samecase stimuli. 1 This would be consistent with findings in the object perception literature in which grouping disrupts attention to the components of a stimulus (e.g., Rensink & Enns, 1995). In the present context, this would generate a novel result in which performance would be better with mixed-case than with single-case stimuli.…”

Closure of salient regions determines search for a collinear target configuration

“…Support for this idea is provided by evidence that perceptual configurations may be detected more efficiently than their isolated features (Pomerantz, Sager, & Stoever, 1977; see also Treisman & Paterson, 1984). In addition, visual search studies have shown that component parts may be grouped prior to the engagement of attention (e.g., Moore & Egeth, 1997;Rensink & Enns, 1995), and that search may be more effectively guided by integrated shapes than by corresponding local features (Found & Müller, 1997). Moreover, there is evidence that early visual, or preattentive, processes operate on the basis of a variety of grouping principlesnotably, similarity (Duncan, 1984;Duncan & Humphreys, 1989;Humphreys, Quinlan, & Riddoch, 1989), closure (Elder & Zucker, 1993;Han, Humphreys, & Chen, 1999a;Kovács & Julesz, 1993), and proximity (Han, Humphreys, & Chen, 1999b).…”

The Influence of Cast Shadows on Visual Search

“…Further work is needed here. (9) 8.2 Locus of processing The existence of a process that impedes rapid access to low-level features is also found in several other aspects of rapid vision, such as rapid grouping, in which the formation of a group impedes access to constituents that support rapid search on their own (Rensink and Enns 1995), and rapid completion, in which completion results in a loss of distinctive features that would otherwise support rapid search (Rensink and Enns 1998). This latter process requires approximately 250 ms (Rauschenberger and Yantis 2001).…”

“…The object of condition 5F was to investigate whether the effect of gaps could be`repaired' by the use of grouping to form a virtual line (see Rensink and Enns 1995). (8) A line element corresponds to a structure without a noticeable surface or volume to it, eg a wire or a thin branch.…”