Shadow processing: Top-down or bottom-up?

G Porter, A Tales, TS Troscianko, Ute Leonards

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

Abstract

The existence of an automatic shadow discounting mechanism in the visual system (Rensink andCavanagh, 2004 Perception 33 1339 ^ 1358) is still under debate (eg Elder et al, 2004 Perception33 1319 ^ 1338). Revisiting Rensink and Cavanagh's search task, we found that, independently ofthe exact task requirements (target-present/target-absent or target-present only), search wasslowed for upright shadow stimuli relative to inverted, but not for a control condition in whichneither stimulus orientation could be interpreted as shadows. Differences emerged consistentlyin absolute reaction times but not search slopes. Similarly, only the number of eye movementsbut not fixation durations increased in the shadow-like condition. Taken together, our data arein line with Rensink and Cavanagh's observation that shadow-like images are difficult to process.However, rather than an automatic bottom ^ up driven mechanism to discount shadows, our datasuggest the existence of a top ^ down mechanism that leads to delayed processing of shadow-like stimuli.[Supported by the BRACE Charity.]
Translated title of the contributionShadow processing: Top-down or bottom-up?
Original languageEnglish
Title of host publicationPerception
Pages161 - 161
Number of pages1
Volume36
Publication statusPublished - 2007

Structured keywords

  • Brain and Behaviour
  • Cognitive Science
  • Visual Perception

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