A psychophysical approach to dimensional separability

Combinations of some physically independent dimensions appear to fuse into a single perceptual attribute, whereas combinations of other dimensions leave the dimensions perceptually distinct. This apparent difference in the perceived distinctiveness of visual dimensions has previously been explained by the postulation of two types of internal representations—integral and separable. It is argued that apparent integrality, as well as its intermediate forms, can result from a single type of representation (the separable type), due to various degrees of correspondence between physical and separable psychological dimensions. Three experiments tested predictions of this new conceptualization of dimensional separability. Experiment 1 demonstrated that a physical dimension corresponding to a separable psychological dimension did not produce interference, whereas a physical dimension not corresponding to a separable psychological dimension did produce interference. Experiment 2 showed that the pattern of results obtained in Experiment 1 could not be accounted for by similarity relations between stimuli. Experiment 3 showed that degrees of correspondence could account for different amounts of interference as well as an inverse relationship between interference and condensation time. These findings imply that previous definitions of integrality are inadequate. Two new converging criteria are proposed, based on the invariance of perceived values on psychological dimensions and on the effect of rotating a configuration of stimuli in a multidimensional space. The present findings furthermore raise the possibility that a single type of internal representation may sufficiently account for all phenomena previously believed to arise from integrality.