Theory of reasoned action
Behavior follows from intention, which is set by attitudes and subjective norms.
What it means
The Theory of Reasoned Action (TRA) holds that behavior is driven by behavioral intention, and that intention is determined by two factors: a person's attitude toward the specific behavior and their subjective norms, meaning the perceived social pressure from important others to perform it or not. The model is grounded in an expectancy-value framework, in which attitudes are built from beliefs about the likely consequences of the behavior weighted by their evaluation, and norms are built from beliefs about what specific referents expect weighted by the motivation to comply. Its key limitation, which directly motivated its successor, is that it assumes the behavior is under full volitional control — a poor assumption for behaviors that require skills, resources, or opportunities the person may lack. The Theory of Planned Behaviour repaired this by adding perceived behavioral control as a third determinant of intention and, sometimes, of behavior directly. TRA remains foundational for predicting deliberate, reasoned behaviors such as voting or purchasing. It matters because it established the now-standard logic that to change behavior you often must first change the beliefs that shape attitudes and norms, and thereby intention.
Examples
Voting intention can be modeled from a person's attitude toward voting plus their sense that family and friends expect them to vote.
A shopper's intention to buy fair-trade coffee is modelled from believing it helps growers (attitude) plus a sense that friends would approve (norms) — a fully voluntary, deliberate choice.
To lift organ-donor sign-ups, a campaign shifts the two things the model names: beliefs about what donation achieves, and the sense that people you respect have already registered.
First described in Fishbein & Ajzen (1975).