Unequal Equal Intervals: A Paradox in the Measurement of Intelligence

Abstract

The hypotheses were that expert judges (e.g., psychologists, social workers, psychiatrists) would perceive intervals of intelligence as follows: (a) Psychometrically equal intervals from different ranges of intelligence (e.g., medium vs low) are judged as psychologically unequal. (b) Traditional boundaries of intellectual categories profoundly influence experts' judgments. (c) Intervals from the higher ranges of intelligence are judged to be relatively larger than equal intervals from the lower ranges. The hypotheses were essentially confirmed. The nature of intelligence from the viewpoint of the expert judge is a series of unequal, ordered categories, with unequal but interval scale measurement characteristics within categories.