Towards a universal scale for perceptual value

This paper addresses the problem of context effects in psychophysical measurement, and how these effects are reflected by MOS values obtained in auditory tests. Based on a simple model of the perception and judgment processes which are relevant in a subjective quality-judgment situation, it advocates for using a universal scale for the value which is related to the perceptual event, and which has a meaning beyond the specific test context. The E-model´s transmission rating scale is considered to be a candidate for such a scale.