Academic journal article Attention, Perception and Psychophysics

Explaining Efficient Search for Conjunctions of Motion and Form: Evidence from Negative Color Effects

Academic journal article Attention, Perception and Psychophysics

Explaining Efficient Search for Conjunctions of Motion and Form: Evidence from Negative Color Effects

Article excerpt

Published online: 19 February 2014

© Psychonomic Society, Inc. 2014

Abstract Dent, Humphreys, and Braithwaite (2011)showed substantial costs to search when a moving target shared its color with a group of ignored static distractors. The present study further explored the conditions under which such costs to performance occur. Experiment 1 tested whether the negative color-sharing effect was specific to cases in which search showed a highly serial pattern. The results showed that the negative color-sharing effect persisted in the case of a target defined as a conjunction of movement and form, even when search was highly efficient. In Experiment 2, the ease with which participants could find an odd-colored target amongst a moving group was examined. Participants searched for a moving target amongst moving and stationary distractors. In Experiment 2A, participants performed a highly serial search through a group of similarly shaped moving letters. Performance was much slower when the target shared its color with a set of ignored static distractors. The exact same displays were used in Experiment 2B; however, participants now responded "present" for targets that shared the color of the static distractors. The same targets that had previously been difficult to find were now found efficiently. The results are interpreted in a flexible framework for attentional control. Targets that are linked with irrelevant distractors by color tend to be ignored. However, this cost can be overridden by top-down control settings.

Keywords Selective attention · Visual search

Human behavior takes place in a complex, cluttered, dynamic environment. The human visual system can not simultaneous- ly process all of this information (see, e.g., Broadbent 1958; Tsotos, 1990). Mechanisms of selection are required in order to prioritize relevant and to deprioritize irrelevant stimuli for further processing and action. The visual search task (see Chan & Hayward, 2013; Wolfe, 1998; Wolfe & Horowitz, 2004, for reviews), in which an observer is required to find a target amongst a set of spatially distributed distractors, has been used extensively to characterize these mechanisms of selection. In the visual search task, the slope of the function relating the number of potential targets to RT (search slope) is the primary measure of the efficiency of a given search. Certain targets may be detected highly efficiently, with little increase of RT as the number of items increases. In the extreme, when the search slope is close to zero, all of the items in a display may be processed in parallel. For example, the visual system is highly sensitive to differences in the gross features of objects; a single red item amongst green items may "pop out" effortlessly from a display, and may be very difficult to ignore (e.g., Theeuwes, 1992; see Theeuwes, 2010,fora review). According to Treisman's feature integration theory (FIT; Treisman & Gelade, 1980; Treisman, 2006) and its derivatives (e.g., Guided Search [GS], Wolfe, 1994, 2007; dimension weighting [DW], Müller, Heller, & Ziegler, 1995; Krummenacher & Müller, 2012), these basic features are represented in distinct feature maps within dimensional mod- ules that code the gross distribution of a particular feature in the environment; thus, these feature maps alone may signal the presence of unique features. In contrast, recovering more detailed information, including how multiple features are con- joined, requires spatial selection, producing search slopes greater than zero, as single items or small groups of items are inspected in turn.

Revisions to this basic FIT architecture allow the feature maps to guide selection even for complex conjunctively defined targets, such as a red X amongst green Xs and red Os (e.g., Treisman & Sato, 1990; Wolfe, 1994; Wolfe, Cave, & Franzel, 1989). Instead of spatial selective attention being deployed at random, selection may be guided toward locations that contain relevant features and away from locations that contain irrelevant features. …

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