SAME-DIFFERENT TEXTURE-DISCRIMINATION IN PIGEONS - TESTING COMPETING MODELS OF DISCRIMINATION AND STIMULUS INTEGRATION

The choice behavior of 6 pigeons performing a multidimensional same-di fferent texture discrimination was examined. On each trial, they had t o choose among 2 choice hoppers depending on whether a color, shape, o r redundant (color and shape) target signal was present or not in a te xtured stimulus. Receiver operating characteristic (ROC) curves were p roduced by variations in the a priori signal presentation probabilitie s across conditions. Quantitative analyses of these ROC curves were us ed to evaluate different competing theories of discrimination (signal detection vs. high-threshold-default response models) and information integration (independent observations, additive integration, unidimens ional models). The results suggested the structure of the pigeons' cho ice behavior in this same-different discrimination was best described by an unequal variance signal detection model involving a unidimension al evidence variable (e.g., degree of difference).