Past reports that humans can, in complete darkness, sense with their fingers the colors of objects have been received with skepticism. A previously proposed hypothesis, based on differential rate of absorption of infrared radiation by different layers of the skin, is inconsistent thermodynamically. Quantitative analysis of the system consisting of a room-temperature surface juxtaposed to the higher temperature skin, however, leads to the conclusion that large differences in emissivity of different room-temperature surfaces almost certainly could be detected by the associated effects on skin temperature. Easily repeatable demonstrations confirm this, and a few simple temperature measurements confirm the theoretical identification of the mechanism. (34 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1966 American Psychological Association.