Elaboration Likelihood Model

The Elaboration Likelihood Model of persuasion (ELM; proposed by Petty & Cacioppo, 1981, 1986) is a model of how attitudes are formed and changed (see also attitude change). Central to this model is the elaboration continuum, which ranges from low elaboration (low thought) to high elaboration (high thought). Depending on the extent of elaboration, different processes can mediate persuasion.

Key Elements
The ELM distinguishes between two routes to persuasion: the Central Route and the Peripheral Route. This implies it is one of a number of dual-process theories of information processing. Central route processes are those that require a great deal of thought, and therefore are likely to predominate under conditions that promote high elaboration. Central route processes involve careful scrutiny of a persuasive communication (e.g., a speech, an advertisement, etc.) to determine the merits of the arguments. Under these conditions, a person’s unique cognitive responses to the message determine the persuasive outcome (i.e., the direction and magnitude of attitude change).

Peripheral route processes, on the other hand, require little thought, and therefore predominate under conditions that promote low elaboration. These processes often rely on judgmental heuristics (e.g., “experts are always right”) or surface features of a message (e.g., the number of arguments presented) or its source (e.g., their attractiveness).

Which route is taken is determined by the extent of elaboration. Both motivational and ability factors determine elaboration. Motivational factors include (among others) the personal relevance of the message topic, accountability, and a person’s Need for Cognition (their innate desire to enjoy thinking). Ability factors include the availability of cognitive resources (e.g., the presence or absence of time pressures or distractions) or relevant knowledge needed to carefully scrutinize the arguments. Under conditions of moderate elaboration, a mixture of central and peripheral route processes will guide information processing.

Additional Propositions
In addition to these factors, the ELM also makes several unique proposals.


 * Attitudes formed under high elaboration are stronger (more predictive of behavior and information processing, more stable over time, more resistant to persuasion) than those formed under low elaboration.
 * Variables can serve multiple roles in a persuasive setting depending on other contextual factors (examples below).
 * Under high elaboration, a given variable (e.g., source expertise) can either serve as an argument (“If Einstein agrees with the theory of relativity, then this is a strong reason for me to as well”) or as a biasing factor (“if an expert agrees with this position it is probably good, so let me see what else agrees with this conclusion” (at the expense of information that disagrees with it)).
 * Under conditions of low elaboration, a given variable can act as a cue (e.g., through the use of an “experts are always right” heuristic – note that while this is similar to the case presented above, this is a simple shortcut, and does not require the careful thought as in the Einstein example above).
 * Under conditions of moderate elaboration, a given variable can serve to direct the extent of information processing (“Well, if an expert agrees with this position, I should really listen to what (s)he has to say”). Interestingly, when a variable affects elaboration, this can increase or decrease persuasion, depending on the strength of the arguments presented. If the arguments are strong, enhancing elaboration will enhance persuasion.  If the arguments are weak, however, more thought will undermine persuasion.

More recent adaptations of the ELM (e.g., Petty, Briñol, & Tormala, 2002) have added an additional role that variables can serve. They can affect the extent to which a person has confidence in, and thus trusts, their own thoughts in response to a message. Keeping with our source expertise example, a person may feel that “if an expert presented this information, it is probably correct, and thus I can trust that my reactions to it are informative with respect to my attitude”. Note that this role, because of its metacognitive nature, only occurs under conditions that promote high elaboration.