Abstract

A mathematical model is developed in an attempt to relate errors in multiple stimulus-response situations to psychological inter-stimulus and inter response distances. The fundamental assumptions are ( a ) that the stimulus and response confusions go on independently of each other, ( b ) that the probability of a stimulus confusion is an exponential decay function of the psychological distance between the stimuli, and ( c ) that the probability of a response confusion is an exponential decay function of the psychological distance between the responses. The problem of the operational definition of psychological distance is considered in some detail.