The Heuristic-Systematic Model of Social Information Processing

Persuasion has been a major topic of study for scholars interested in attitude change. Earlier cognitive theories focused on how people process the quality of persuasion messages. For example, persuasion effects were conceptualized in terms of the attention allocated to the message, the comprehension of the message content, and the acceptance of the message conclusions. Unlike these message-based theories of persuasion, the Heuristic Systematic Model (HSM), together with the Elaboration Likelihood Model (ELM) (Petty & Cacioppo, 1981, 1986b), recognized a host of variables conceptually independent of message quality that influence people. Most importantly, according to the HSM and the ELM, these variables can trigger qualitatively different information processing. 

Although people can carefully attend to and elaborate on the content of a persuasion message, they can also process the message quite superficially, attending only to cues peripheral to its content, such as the length of the message and the sources of the message. The HSM attempts to characterize these two modes of processing - systematic and heuristic - and to specify the conditions that trigger and govern a specific mode of processing. We hasten to add that the two modes of information processing (systematic vs. heuristic) are not linked in a one-to-one fashion with the types of informational cues (message content vs. other cues), as suggested by some researchers (Kruglanski & Thompson, 1999). The critical assumption of the HSM is that people can engage in systematic or heuristic processing. People can scrutinize cues peripheral to the message content, or they can process the message content heuristically. The HSM is a dual-process model (Chaiken & Trope, 1999) positing two concurrent modes of qualitatively different social information processing. 

The HSM has undergone several major developments. Initially, the model specified the two modes of heuristic and systematic processing (Chaiken, 1980, 1987). Then, the model was extended to specify the psychological conditions for triggering the modes of processing in terms of the discrepancy between actual and desired subjective confidence (Chaiken, Liberman, & Eagly, 1989). Finally, in addition to the accuracy motivation assumed to be present in most persuasion situations, the HSM was extended to include two other types of underlying motivations: defensive and impression motivation (Chaiken, Giner-Sorolla, & Chen, 1996). As a general model of social information processing, the HSM has been applied to a wide range of phenomena (e.g., Bohner, Moskowitz, & Chaiken, 1995).