The use of units such as the foot and the mile, which are obviously of physiological origin, indicates that physical measurements are based on direct human experiences. The definitions of many fundamental physical quantities have resulted from attempts to quantify direct sensory experiences. Thus, our scale of masses has grown from the distinction “heavier‐lighter”; our temperature scale from “hotter‐colder”; our light intensity scale from “brighter‐dimmer”. It is true that the physicist has, to a large extent, replaced these personal judgments by the pointer readings or the counts given by quantitative instruments, but surprisingly accurate quantitative measurements may be made by the human organism without the aid of such instruments. In comparing the human meter with devices which the physicist is more inclined to trust, we shall find it advisable to set up a parallelism between the terms used by the physicist and those used by the psychologist. The signal supplied to a meter is exactly analogous to the stimulus to which the human reacts. The ordinary meter yields its measurement in terms of a pointer reading, the human meter indicates the magnitude of the stimulus by some sort of a motor or verbal response.