Many animal preference experiments involve test stimuli that have been chosen by the experimenter to represent different strengths of a single attribute. It is assumed that the animals also scale the test stimuli along a single dimension. This paper shows how it is possible to use the
'Unfolding Technique' developed by Coombs(1964) to check the validity of this assumption. A simple experiment is described which used Coombs' technique to verify that three visual test stimuli were ranked by laboratory rats along a single dimension. These stimuli were subsequently used in
an experiment to see how different housing conditions changed rats' preferences for visual complexity.