ABSTRACT
As we have seen, a straightforward procedure for dividing a continuum into equal-appearing intervals is to allow an observer to adjust a series of stimuli to match his conception of equal distances. That was Plateau's procedure when he asked eight artists to paint a middle gray between black and white. The result was a partition scale. But partition scales also come in other varieties. Some of them even turn up in experiments for which the investigator did not intend to produce partitionings. Yet regardless of their origin, all partition scales have one hallmark in common: compared to the magnitude scale, the partition scale is nonlinear. When the partition scale is plotted against the magnitude scale, the result is a curve that is concave downward.
