ABSTRACT
It is proposed that multiple stimulation is the rule in space and motion perception because potential cues become stimuli through simple learning that takes place when a potential cue occurs simultaneously with the perceptual variable it eventually conies to evoke. If such learning readily occurs, instances of previously unknown duplicating stimulation may yet be discovered. An experiment is eited that serves as an example, it demonstrated that the slope of the line of regard with which an object on the ground is seen serves as a cue for its distance from the eyes. Presumably, the slope of regard had often occurred while other stimulation caused perceptions of distance of objects on the ground and had become a stimulus for distance.
A similar kind of learning may be responsible for duplicating stimulation in stcrcoscopie depth perception, which consists in the differences in configuration in the two eyes that accompany retinal disparity. Because ordinarily such binocular configurational differences are inseparable from retinal disparities, their effectiveness was only recently discovered, and that was possible only because one kind of configurational difference is more effective than another kind. The greater effectiveness of one kind may result from more numerous learning opportunities.
