Indices of response bias in the same-different experiment

The same-different experiment is popular for assessing Perceptual Performan ce, including the performance of people with neuropsychological deficits. A lthough the measurement of accuracy with this experiment is now well unders tood, the measurement of response bias remains problematic. Reformulating t he decision space for the experiment can yield new bias indices that are an alogous to, but numerically different from, those of the more familiar yes- no experiment. Isobias curves that show how hit rate covaries with false al arm rate for constant bias but varying accuracy are presented for eight ind ices, and best-fitting parameters of the isobias functions are determined f or a set of experimental data. The theoretical status of the bias indices a nd their relation to other formulations are reviewed.