Most theories of health behavior share a belief that the single
best predictor of an individual's behavior is simply his/her
intention to engage in that behavior. Thus, virtually all
health-behavior theories include some version of
the construct of behavioral intention (BI) as a proximal antecedent
to action. The most often cited of these theories is the Theory
of Reasoned Action (TRA; Fishbein
& Ajzen, 1975), which has BI as its focal antecedent.
Together with its offshoot, the Theory of Planned
Behavior (TPB; Ajzen,
the TRA illustrates many of the issues surrounding the conceptualization
and measurement of intentions and other proximal antecedents
to health behavior.
The TRA is one of a group of psychosocial theories of human
social behavior referred to collectively as expectancy
value theories (Feather
& Newton, 1982;
name reflects a process thought to precede all behaviors:
Decisions to act or not act are the result of an assessment
of the likelihood of specific outcomes associated with the
act along with the subjective value assigned to those outcomes.
When the assessment produces a positive evaluation, a decision
is made (usually) to act. That decision is the BI, which is
the only proximal antecedent to behavior in the TRA and TPB.
Specific antecedents to BI in the TRA and TPB are subjective
norms (what important others want one to do) and attitudes
toward the behavior (e.g., one's affective reaction to performance
of the behavior).
Definition. Intentions have been defined in the
TRA/TPB as: the amount of effort one is willing to exert to
attain a goal (Ajzen,
"behavioral plans that...enable attainment of a behavioral
simply "proximal goals" (Bandura,
1997). The measures section presents examples of
BI measures (guidelines for construction of these measures
can be found on the TPB webpage; Ajzen,
In essence, intentions can be conceived of as goal
states in the expectancy value tradition that are
the result of a conscious process that takes time, requires
some deliberation, and focuses on consequences (Loewenstein,
Weber, Hsee, & Welch, 2001).
Predicting behavior. The TRA has done a very good
job in predicting health behavior. In particular, meta-analyses
have shown that intentions account for between 20% and 30%
of the variance in health behaviors (Albarracin,
Johnson, Fishbein, & Muellereile, 2001; Armitage
& Conner, 2001; Conner
& Sparks, 2005; Hagger,
Chatzisarantis, & Biddle, 2002; Sheeran,
& Orbell, 1998).