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Matthew Hilchey, Mark Mills, Jay Pratt; Dissociating spatial orienting biases from selection demands with eye movements. Journal of Vision 2018;18(10):1198. doi: https://doi.org/10.1167/18.10.1198.
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There is ambiguity surrounding whether attentional orienting is biased in favor of or against locations that were previously attended in two-forced choice stimulus discrimination tasks. In the simplest case, a target appears abruptly in a distractor-less environment and its location randomly repeats from moment-to-moment. Here, there are response repetition tendencies whenever the target location repeats and roughly equal tendencies to switch from the prior response whenever the prior target location switches. These opposing effects equivocate whether there are orienting biases. In more complex cases, a unique target color is embedded in an array of homogenous distractors colors; once found, its shape is discriminated with a manual response. These "priming of pop-out" studies show faster responding overall whenever the target location repeats, suggesting that attention may be biased in favor of the prior target location. However, the magnitude of these positive position priming effects is determined by whether the response repeats, such that there is often little to no effect when the response switches. Thus, here too it is unclear to what extent position priming reflects an attentional orienting bias. In this study, we resolve this ambiguity. In our first set of experiments, four diamonds form an imaginary square centered on a fixation stimulus. The target diamond is a color singleton, and once found, its shape is discriminated. The findings reinforce prior observations showing that positive position priming is response-mediated. Our hypothesis is that position priming is tied to the effector making the discrimination judgment. If so, then we should observe an orienting bias in the eyes that is not contaminated by the processes involved in making manual discrimination judgements. Therefore, in our second set of experiments, we require eye movements to each target prior to the manual discrimination response and we find an orienting bias.
Meeting abstract presented at VSS 2018
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