Can Psychology do Without Private Data

The behaviorist attack on the use of introspection as a source of data in psychology is an oft told tale. It was an essential part of the early behaviorist program that psychology was to be an “objective” science of the behavior of organisms, and that as a condition of that objectivity it must draw its evidence from “public” sources. Any bit of evidence adduced must be in principle equally available to any qualified observer. This has the practical effect of ruling out private data of “consciousness” — sensory qualia, mental imagery, qualities of feeling, contents of covert thinking — which by the nature of the case are directly experienceable by one and only one person. It thereby restricts the evidential basis of psychology to reports of the overt behavior of organisms, plus facts about the physical situation of that behavior.