A direct test of the unequal-variance signal detection model of recognition memory
Analyses of the receiver operating characteristic (ROC) almost invariably suggest that, on a recognition memory test, the standard deviation of memory strengths associated with the lures (σlure) is smaller than that of the targets (σtarget). Often, σlure/σtarget ≈ 0.80. However, that conclusion is based on a model that assumes that the memory strength distributions are Gaussian in form. In two experiments, we investigated this issue in a more direct way by asking subjects to simply rate the memory strengths of targets and lures using a 20-point or a 99-point strength scale. The results showed that the standard deviation of the ratings made to the targets (starget) was, indeed, larger than the standard deviation of the ratings made to the lures (slure). Moreover, across subjects, the ratioslure/starget correlated highly with the estimate of σlure/σtarget obtained from ROC analysis, and both estimates were, on average, approximately equal to 0.80.
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