THE OPTIMUM DECISION RULES IN THE SAME-DIFFERENT PARADIGM

In this paper we derive the optimum (likelihood-ratio) decision statis tic for a same-different paradigm. The likelihood ratio is dependent o n the degree of correlation between the two observations on each trial . For the two extreme cases in which the observations are either indep endent or highly correlated, the optimum decision rule is identical to each of two previously suggested decision rules. For these two cases, the receiver-operating characteristic (ROC) curves are calculated. Fi nally, an experimental procedure is suggested for assessing the decisi on rule actually used by the observer in a same-different task.