An empirical investigation of Coombs' unfolding theory was conducted i
n which basic assumptions of the theory were tested. The primary conce
rn was to investigate the effects upon individuals' preference judgeme
nts when the presented set of scaled stimuli was changed. Two types of
judgemental tasks were used to assess these possible contextual effec
ts: rank order and paired comparisons, and two different sets of scale
d stimuli were presented. A reliability measure was also taken as appa
rent context effects could merely be due to lack of reliability. The o
btained data supported the basic assumptions of Coombs' theory, and su
bjects' responses were highly reliable, thus little confounding should
have occurred. The change of context effects, however, were contrary
to the prediction of Coombs' theory. Strong evidence for these context
effects was found for both sets of stimuli and both kinds of tasks im
plemented. Implications of these findings are discussed and doubts are
raised concerning the usefulness of the unfolding theory in the conte
xt of attitude scaling.