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Jonathan Peirce; Is it just motion that silences awareness of visual change?. Journal of Vision 2012;12(9):112. doi: 10.1167/12.9.112.
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Suchow and Alvarez (2011) present a compelling illusion in which subjects fail to notice changes in a rotating array of elements that are quite obvious in a similar static array. Awareness of changes to the element size, colour, luminance and shape can all be ‘silenced’ in this manner. This appears to indicate that the perception of motion is of particular importance to the visual system, such that the presence of a moving stimulus completely dominates our visual attention. We wondered whether the converse effects are possible; whether salient, coherent changes in some other dimension, such as colour or size, are able to silence our awareness of motion. We also wanted to generate a 2AFC task, in which subjects made judgements about the rate of change, rather than having subjects make a judgement about how strong they felt the effect was. This enables us to test naïve observers, since we don’t need to explain the effect to them. Subjects were presented with two circular annuli of dots that were changing in some dimension (size, colour or position). One of the stimuli was also exhibiting some additional ‘distracting’ change in one of the three dimensions (but not the task dimension). Subjects reported which of the two stimuli was changing most rapidly in the task dimension. Using a 2AFC task and a staircase procedure the point of subjective equality (PSE) was determined. The PSE was very substantially shifted in all cases to indicate a silenced awareness of the change in the distracting stimulus, regardless of whether that distraction was a coherent motion, coherent size change or coherent colour change. Motion, it seems, is not special in its ability to silence awareness; coherent changes in colour or size can also silence our awareness of incoherent dot motion.
Meeting abstract presented at VSS 2012
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