R. C. Grace and H. I. Savastano (2000) have devised a procedure to determin
e whether the effectiveness of a stimulus as a conditioned reinforcer depen
ds on the temporal context of reinforcement. Although they interpret their
results in terms of the contextual choice model, which maintains that value
is independent of context, the results also support delay-reduction theory
, which maintains that value depends an temporal context. It is argued that
the delay-reduction view of the role of temporal context is also intuitive
ly more plausible and more consistent with the way choice responds to chang
es in conditions.