Heuristic-Systematic Model of Persuasion

Definition

The heuristic-systematic model is a theory of persuasion that suggests attitudes can change in two fundamentally different ways. One way is through systematic processing, whereby people think carefully about any available information when forming an opinion to determine whether the information is accurate or valid. Attitudes are then based on the conclusions from this careful consideration of the facts. However, this kind of thinking takes a lot of effort, and given that people usually only have limited time and ability to think carefully, the heuristic-systematic model suggests that attitudes are often formed in a more simplified manner. This simplified form of attitude judgment is called heuristic processing, and it involves using rules of thumb known as heuristics to decide what one's attitudes should be. This model of persuasion has received a great deal of empirical support in the social psychology research literature and has had a major impact on applied fields of research like health behavior and consumer behavior.

Common Heuristics

A number of different persuasion heuristics can be used to form opinions. For instance, when using the consensus heuristic, attitudes are simply based on the opinions that the majority of other people hold. In this case, people infer that “if everybody believes something, then all those people must be right.” For example, a political speech might be more convincing when a lot of people in the audience clap than when fewer people clap, and a consumer product might seem better when it is the last one left on the shelf. The expert heuristic is another simple basis for determining attitudes. In this case, attitudes are based on the opinions or recommendations of trusted and knowledgeable experts. The inference here is that “experts are usually right.” For instance, if a dentist recommends a certain type of toothpaste for fighting cavities, then it must work, or if astronauts drink Tang for breakfast, then it must be good or nutritious. Finally, the length of the message itself can be used as a rule of thumb for persuasion, even without thinking carefully about the information the message contains. The message length heuristic suggests that longer messages, which seem to contain a lot of arguments, are more convincing because people infer that the length of the message implies it is strong or correct (i.e., length implies strength). For instance, the same essay might be more convincing when presented in double-spaced format than when it is in single-spaced format, even though the content of the essay is exactly the same in both instances. Importantly, the model suggests that heuristic rules of thumb are only used to the degree that the rule seems valid and reliable. Not everyone thinks experts are always right, and in such cases, people are obviously less likely to follow expert advice. Also, the consensus heuristic may be called into question when a political poll is based on a very small number of respondents, in which case people tend to stop using this heuristic.

Bias in Persuasion

The heuristic-systematic model suggests that opinions can be biased in a number of different ways. For instance, heuristic rules can bias the thoughts that people have when they are thinking carefully about an issue (i.e., heuristics can bias systematic processing). This is the case, for instance, when an argument seems more likely to be correct or persuasive because it comes from an expert compared to when the same argument comes from a less impressive information source. For instance, arguments suggesting that Acme brand is the best on the market seem more likely to be true when these arguments come from an expert source like Consumer Reports magazine than when the same arguments come from a less credible source like Wal-Mart.

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