How Stage Theories Can Be Tested
A variety of approaches have been used to determine whether a particular behavior
change passes through the sequence of stages proposed by a stage theory
(Weinstein, Rothman, et al., 1998). The most common approach is to use crosssectional
data from surveys or questionnaires to look for differences among people
thought to be in different stages. Simply finding differences among stages tells
us little, however, since nonstage processes will also produce such differences. Finding
specific hypothesized characteristics of people in various stages is more convincing.
Another test sometimes used to verify a stage theory is to compare the
success of an intervention that is tailored to a person’s stage with a standardized
intervention. This is also a poor test. Tailoring usually involves considerable personalization
and extra attention, and the latter ingredients, rather than the tailoring,
could easily account for greater success in the tailored condition.
Much more definitive are experimental studies using matched and mismatched
interventions. If it is true that different variables influence movement at
different stages, treatments designed to influence these variables should be most
effective when applied to people in the appropriate stage. Thus, individuals in a
given stage should respond better to an intervention that is matched to their stage
than to one that is mismatched (that is, matched to a different stage).
Only stage models predict that the sequencing of treatments is important. For
maximum effectiveness, the order of interventions should follow the hypothesized
order of stages. Consequently, sequence effects provide further evidence of a stage
process. Unfortunately, because testing for sequence effects requires sequential