Psychophysics Phenomenologized? Sensation and Decision in Visual Motion Perception

Abstract

Experimental phenomenology and psychophysics are two rather different approaches to the study of perception, and rely on first-person descriptions and third-person measurements of the percept, respectively. Yet, a common ground may be found in the original goal, shared by both approaches, of addressing the conscious dimension of perception. Here we argue that, despite being objective and quantitatively-oriented, psychophysics can, with some cautions, recover certain simple subjective aspects of conscious perception. Building upon the results of a motion perception experiment, we show how to transform the ratings of subjective visibility into a well-known index of objective discriminability in perceptual decisions (d’). We found that, once all factors are equated, motion discrimination is superior to motion detection, as measured as perceptual decisions; in turn, motion detection is superior to subjective motion visibility. This finding strengthens our previous suggestion that, under uncertainty conditions, perceptual decisions can be taken before the conscious percept is fully stabilized, and suggests that some simple sensations can be reliably captured by objective “currency” through an open-minded quantitative approach. Our perspective may be regarded as an attempt to “phenomenologize psychophysics”.