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Features in visual search combine linearly

Pramod, RT and Arun, SP (2014) Features in visual search combine linearly. In: JOURNAL OF VISION, 14 (4). pp. 1-20.

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Official URL: http://dx.doi.org/10.1167/14.4.6


Single features such as line orientation and length are known to guide visual search, but relatively little is known about how multiple features combine in search. To address this question, we investigated how search for targets differing in multiple features ( intensity, length, orientation) from the distracters is related to searches for targets differing in each of the individual features. We tested race models (based on reaction times) and coactivation models ( based on reciprocal of reaction times) for their ability to predict multiple feature searches. Multiple feature searches were best accounted for by a co-activation model in which feature information combined linearly (r = 0.95). This result agrees with the classic finding that these features are separable i.e., subjective dissimilarity ratings sum linearly. We then replicated the classical finding that the length and width of a rectangle are integral features-in other words, they combine nonlinearly in visual search. However, to our surprise, upon including aspect ratio as an additional feature, length and width combined linearly and this model outperformed all other models. Thus, length and width of a rectangle became separable when considered together with aspect ratio. This finding predicts that searches involving shapes with identical aspect ratio should be more difficult than searches where shapes differ in aspect ratio. We confirmed this prediction on a variety of shapes. We conclude that features in visual search co-activate linearly and demonstrate for the first time that aspect ratio is a novel feature that guides visual search.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the ASSOC RESEARCH VISION OPHTHALMOLOGY INC
Keywords: perception; dissimilarity; object recognition; salience
Department/Centre: Division of Biological Sciences > Centre for Neuroscience
Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 16 Jul 2014 09:46
Last Modified: 16 Jul 2014 09:46
URI: http://eprints.iisc.ac.in/id/eprint/49474

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