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Amrita Puri, David Whitney, Charan Ranganath; Facilitatory effects of expectation on object discrimination. Journal of Vision 2008;8(6):136. doi: 10.1167/8.6.136.
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© ARVO (1962-2015); The Authors (2016-present)
Although it is well known that expectation of low-level attributes (locations and features) can facilitate processing of simple visual stimuli, less is known regarding effects of expectation on processing of more complex, real-world stimuli. Here, a series of experiments reveals effects of object category expectation on performance of a visual discrimination task. Participants viewed morphed images composed of varying ratios of pairs of faces or places and indicated which original face or place dominated each image. Cues preceding each image could be valid (60% of trials), neutral (20% of trials) or invalid (20% of trials) with respect to object category. Performance was measured across a range of difficulty levels, generating separate psychometric and chronometric functions for each validity condition. Valid cues resulted in faster reaction times (RTs) relative to neutral and invalid cues, and steeper psychometric functions relative to the invalid condition, indicating facilitated discrimination after valid category expectation. Inspection of the chronometric functions confirmed that the RT facilitation does not reflect priming of the response. Furthermore, this expectation-dependent facilitation could not be explained by attention to spatial location or to low-level stimulus attributes. These findings demonstrate that expectation at the level of object categories can facilitate processing of complex visual stimuli.
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