Send to

Choose Destination
See comment in PubMed Commons below
J Mem Lang. 2014 Jan;70:36-52.

Validating the unequal-variance assumption in recognition memory using response time distributions instead of ROC functions: A diffusion model analysis.

Author information

University of Massachusetts Amherst.
Ohio State University.


Recognition memory z-transformed Receiver Operating Characteristic (zROC) functions have a slope less than 1. One way to accommodate this finding is to assume that memory evidence is more variable for studied (old) items than non-studied (new) items. This assumption has been implemented in signal detection models, but this approach cannot accommodate the time course of decision making. We tested the unequal-variance assumption by fitting the diffusion model to accuracy and response time (RT) distributions from nine old/new recognition data sets comprising previously-published data from 376 participants. The η parameter in the diffusion model measures between-trial variability in evidence based on accuracy and the RT distributions for correct and error responses. In fits to nine data sets, η estimates were higher for targets than lures in all cases, and fitting results rejected an equal-variance version of the model in favor of an unequal-variance version. Parameter recovery simulations showed that the variability differences were not produced by biased estimation of the η parameter. Estimates of the other model parameters were largely consistent between the equal- and unequal-variance versions of the model. Our results provide independent support for the unequal-variance assumption without using zROC data.


diffusion model; recognition memory; unequal variance

PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for PubMed Central
    Loading ...
    Support Center