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Andrei Gorea, Patrick Cavanagh, Joshua Solomon; On successive memories. Journal of Vision 2012;12(9):859. doi: 10.1167/12.9.859.
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Once having reproduced from memory a stimulus-feature (the standard) and in the presence of this reproduction, is a subsequent decision on a probe being identical to or different from the standard made exclusively with respect to this reproduction, or is it also based on information not used during the reproduction task? If the latter, what’s the nature of this information? A randomly oriented 1.5 cpd Gabor (the standard) was briefly (200 ms) presented on one side of fixation. Observers then attempted to reproduce its orientation (S) by rotating another Gabor (the match), subsequently presented on the opposite side of fixation. Once satisfied with the match’s orientation (M) that remained visible, they were presented at the location of the standard with a probe Gabor whose orientation (P) was either identical with (50% of trials) or different from S by one of 5 ΔS values held constant within each block of trials. Observers had to decide whether P=S ('Same') or P≠S ('Different'). ‘Same’/’Different’ judgments in this latter task were largely determined by the difference between P and M. However, for any given P-M difference the frequency of 'Same' responses was larger on P=S than on P≠S trials. A model where the trial-by-trial decision criterion is inversely proportional to observer’s confidence in his match (i.e. proportional to the memory noise), predicts well the observed performances. It implies trial-by-trial (introspective) knowledge of a non-static memory noise (s). Observers modulate their decision criteria according to their trial-by-trial confidence (proportional to memory noise). This translates into adopting a more conservative criterion on trials where Probe ≠ Standard than on those where Probe = Standard. These criterial shifts can be observed only by reference to the Match; they remain immaterial in a standard Y/N experiment.
Meeting abstract presented at VSS 2012
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