Tests of the abilities to judge ratios of extensive and intensive sensory magnitudes.

The assumption that people are able to numerically judge ratios of sensory magnitude is often used to scale sensations. In this study, we tested this assumption for the extensive sensation of length and the intensive sensations of heaviness and brightness. A ratio model fit judged length ratios accurately and fit judged heaviness and brightness ratios inaccurately. Also, most participants could not judge brightness ratios, even if they seemed able to respond nonverbally to the brightness ratios. These results suggest that people may generally be able to judge extensity ratios but not intensity ratios. Participants used auxiliary judgment operations to compensate for their lack of ability to judge intensity ratios. These auxiliary, nonratio operations were found to yield linear scales of intensive sensory magnitude.