ABSTRACT
Stimuli, such as colors, shapes, or sounds, that are not taken to refer to quite different things beyond themselves we shall refer to as nonsymbolic stimuli. Data obtained from experiments using such stimuli characteristically depend in strong and orderly ways on physically specifiable parameters of those stimuli. This is true for such diverse tasks as absolute identification, naming, c1assification, sorting, discrimination, generalization, paired-associate learning, recognition memory, and comparative judgment. Quite generally , as we reduce the separation between two stimuli along the physical dimensions on which they differ, substitution errors, number of ., same" judgments, discriminative reaction times, and judged similarities increase monotonically until the two stimuli can no longer be discriminated at all. The regular dependency of behavioral data on properties of the physical stimuli appears to demonstrate the importance of perceptual processes in all of these tasks.
