Recent studies have generated a four-system structure proposed as a replacement for Sokolov's unitary OR concept. This conceptualisation developed from a logical consideration of stimulus-response relationships based upon mean response magnitudes over subjects, and paid no attention to individual response types. It is conceivable that no individual subject exhibited responses compatible with such a formulation. This paper addressed that problem by using factor analysis as a means of descriptively summarising the data of each subject, and examining its compatibility with both unitary and four-system structures. Of 72 subjects, none exhibited a factor structure compatible with Sokolov's unitary concept, while 70 exhibited structures compatible with the four-system structure. These results support the validity of the structure proposed to replace the unitary OR. © 1979.