Published online by Cambridge University Press: 06 October 2014
This paper considers the question “What is a psychological unit?”. The ubiquity of units in daily life and in science is considered. The assumption that the individual human being or animal is the psychological unit is examined and rejected. The units represented by the data collected in operant laboratories are interpreted as a subset of the well-defined changes that individual human beings or animals can bring about. The departure of this interpretation from the traditional interpretation in terms of the behaviour of the organism is acknowledged. The paper concludes by noting the relation of the present interpretation of operant research to the problem of identifying psychological units.