Vested interest (Crano, 1983;[1] Crano & Prislin, 1995;[2] Sivacek & Crano, 1982[3]) is a communication theory that seeks to explain how an attitude of self-interest can affect behavior; or, in more technical terms, to question how certain hedonically relevant (Miller & Averbeck, 2013)[4] attitudinal dimensions can influence and consistently predict behavior based on the degree of subjective investment an individual has in a particular attitude object.
As defined by William Crano, vested interest refers to the degree to which an attitude object – an idea, concept, or value with potential emotional interest – is deemed hedonically relevant by the attitude holder. According to Crano, "an attitude object that has important perceived personal consequences for the individual will be perceived as highly vested. Highly vested attitudes will be functionally related to behavior" (Crano, 1983). Simply put, when people are more emotionally or psychologically invested in the results of an object (like a law or policy that may greatly affect them), they will behave in a way that directly supports or defies the object to protect their own self-interest.
For example, a 30-year-old learns that the legal driving age in his state is being raised from 16 to 17. While he may not agree with this proposed change, he is not affected as much as a 15-year-old would be and is unlikely to protest the change. A 15-year-old, however, has much more to lose (waiting another year to get a driver license) and is more likely to strongly oppose the proposed law. To gather support for his position, the 15-year-old might tell other soon-to-be drivers about the new law, so that they collectively have a vested interest in perhaps changing the law. This example illustrates how highly vested attitudes concerning issues depend on the individual's point of view.
Another example of vested interest can be found in a study conducted by Berndsen, Spears and van der Pligt,[5] which involves students from a University in Amsterdam where the teaching faculty proposed the use of English to teach the curriculum instead of Dutch. Vested interest, in this case, suggests that students would be opposed to the use of English rather than Dutch simply based on the potential impact lectures conducted in English might have on their grades.[5]