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Sevda Agaoglu, Bruno Breitmeyer, Haluk Ogmen; Attention and Metacontrast Masking do not Interact. Journal of Vision 2016;16(12):1267. doi: 10.1167/16.12.1267.
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© 2017 Association for Research in Vision and Ophthalmology.
The visual system is flooded with sensory information. Only a subset of this information is selected and stored temporarily for further processing. Visual masking and spatial attention are two of the processes that control the information transfer from sensory memory to short-term memory. A natural question is whether these processes interact or operate independently. Earlier studies suggested that metacontrast masking and common-onset masking interact with attention. However, recent studies reported no interactions between attention and common-onset masking, and pointed out that the earlier studies suffered from ceiling and/or floor artifacts. Our analysis of previous studies reporting metacontrast-attention interactions revealed similar problems. Hence, we investigated metacontrast-attention interactions by using an experimental design in which ceiling/floor effects are avoided. Observers fixated at the center of the display and reported the orientation of a target bar. We manipulated attention by set-size; i.e., the number of oriented bars, presented around a virtual circle, was either two or six. The target bar was indicated by a surrounding ring (metacontrast masking) or a small neighboring cue (baseline). We adjusted target-mask luminances for each observer separately to avoid ceiling (performance in the baseline) and floor (chance level) effects. The stimulus onset asynchrony between the target and the mask (or the cue) was varied to fully capture the classical U-shaped masking functions. Response errors were computed as the difference between the actual and reported orientations. We investigated masking-attention relations by analyzing two different aspects of performance: (i) The mean absolute response-errors, and (ii) the statistical distribution of signed response-errors. Our results show that attention and masking modulate observers' responses without interacting with each other, suggesting that they are independent processes. Statistical modeling of the distribution of signed response-errors also suggests that attention and masking exert their effects by independently modulating the probability of "guessing" behavior.
Meeting abstract presented at VSS 2016
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