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Yuan-Chi Tseng, Joshua Glaser, Eamon Caddigan, Alejandro Lleras; How recent visual experience modulates what we look at first. Journal of Vision 2011;11(11):256. doi: 10.1167/11.11.256.
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When searching for an oddball target, the stimulus in the preceding trial influences performance on the current trial. Responding to a target among two distractors on the current trial is faster when the preceding trial had the same target and distractors colors than when the target and distractor colors were switched (priming of Pop-out, PoP). Finding the oddball is also faster when the preceding trial has no oddball and all elements share the same color with the current distractors, compared to when they share that of the target (distractor previewing effect, DPE). These inter-trial effects are understood in terms of two possible processes: (I) a bottom-up modulation of stimulus visibility, or (II) a top-down modulation on the prior expectation of the oddball feature. Here, we combined these two tasks in a saccade choice experiment (1600 trials) and fit our data with a diffusion model. The drift rate and the thresholds of the diffusion process reflected stimulus visibility and prior target expectation, respectively. All observers showed robust PoP and DPE effects. The best fitting parameters of the diffusion model were compared to unveil the possible modulations underlying PoP and DPE in each participant. The shorter latencies in PoP when the oddball color is repeated may be explained by an increase in target drift rate as well as a smaller decrease in target decision threshold. The model also strongly suggests that the distractor preview condition is associated with a smaller increase in distractor drift rate and a more robust and substantial decrease in threshold, accounting for changes to saccade latencies and accuracy in the DPE. The data and modeling show how a modulation of the same nature (albeit in different directions) underlies these inter-trial effects: repeating a target feature increases its visibility whereas feature status (target or distractor) modulates attentional decision thresholds.
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