Perception in the absence of attention: Can optical illusions provide evidence for perceptual organisation under conditions of inattention?

Hannaford, Josie (2014) Perception in the absence of attention: Can optical illusions provide evidence for perceptual organisation under conditions of inattention? University of West London. (Unpublished)

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Abstract

Theories of visual perception posit that before attention is allocated within a scene, visual information is parsed according to Gestalt principles of organisation (Treisman, 1986). This assumption is challenged by theorists asserting that no parsing occurs in conditions of inattention (Mack & Rock, 1998). In this study, participants distinguished between lengths of two parallel lines, embedded within a dot matrix, forming the Müller-Lyer illusion in experimental trials, compared to no-illusion trials (control condition). It was hypothesised that participants would not be consciously aware of the illusion yet demonstrate decreased accuracy of length judgements. In line with the hypothesis, participants showed decreased accuracy in optical illusion trials, while explicitly being unaware of it. This suggests that participants grouped the dots through adherence to Gestalt principles of organisation, therefore confirming the notion that perceptual organisation occurs in conditions of inattention. This supports studies looking at perceptual organization as existing separate from attention.