Elaboration likelihood model
Persuasion travels two routes: central (argument) and peripheral (cues).
What it means
The Elaboration Likelihood Model (ELM) is a dual-route theory of persuasion holding that the way a message changes attitudes depends on the recipient's 'elaboration likelihood' — how much they are motivated and able to think carefully about its content. When elaboration is high, people take the central route, scrutinizing the quality of the arguments, and the attitudes formed this way tend to be strong, persistent, resistant to counter-persuasion, and predictive of behavior. When motivation or ability is low, people take the peripheral route, relying instead on simple cues such as source attractiveness, credibility, the sheer number of arguments, or mood, producing attitudes that are weaker and more transient. The mechanism turns on factors like personal relevance, distraction, need for cognition, and expertise, which determine how much cognitive effort the recipient invests. A nuance is that the same variable (for instance, source expertise) can function as a central argument, a peripheral cue, or a factor that biases elaboration, depending on the conditions. It matters for advertising, health and political communication, and education, because it specifies when to invest in argument quality versus surface cues and why durable persuasion requires engaging careful thought.
What the evidence shows
The founding demonstration is Petty, Cacioppo and Goldman's 1981 experiment: students read strong or weak arguments for campus exams, attributed to an expert or non-expert source, framed as taking effect next year (high relevance) or in a decade (low relevance). Under high relevance, argument quality drove attitudes; under low relevance, source expertise did. Carpenter's 2015 meta-analysis found the predicted interaction, with argument quality mattering more under high elaboration, though the moderation was modest. But the picture is not clean. A 2018 replication of the 1981 study failed to reproduce its signature interaction, and a need-for-cognition version replicated only under conditions close to the original method, not looser ones. The effect appears real but fragile to procedure.
The strong-argument problem
The model's central prediction rests on a term it never independently defines: argument quality. In practice, strong and weak arguments are identified by pretesting, so a strong argument is simply one that produces favorable thoughts when people think carefully about it. Critics from Stiff and Mongeau onward have argued this makes the core claim close to circular and hard to falsify: if scrutiny fails to boost a supposedly strong message, one can always reclassify the arguments after the fact. Later work has tried to anchor quality in normative standards of good reasoning, with mixed success. The practical cost is that the theory tells you elaboration matters but offers little advance guidance on what will actually count as compelling to a particular audience.
One route or two?
Whether persuasion truly runs on two qualitatively different mechanisms is contested. Kruglanski and Thompson's 1999 unimodel argues that arguments and peripheral cues are not processed differently in kind; both are simply evidence from which a person draws a conclusion, and the apparent two routes reflect how experiments have historically made arguments long and effortful while making cues short and easy. On this view a single judgmental process, varying in how much processing occurs, explains the data. Defenders of the ELM reply that the qualitative distinction still predicts outcomes the unimodel cannot, particularly the greater durability and behavioral force of centrally formed attitudes. The debate remains open, but for practitioners the operational lesson survives it: how hard your audience thinks changes what moves them.
Using it in practice
The model's enduring value is diagnostic: it tells you to match the message to the audience's likely elaboration rather than assume everyone weighs evidence. When motivation and ability are high, as in a costly, personally relevant decision or an expert audience, invest in genuine argument quality, because cues will be scrutinized and durable attitudes require substance. When elaboration is low, as with background media, low-stakes choices, or distracted readers, surface features such as credibility, production polish, or the sheer number of reasons carry more weight, but the resulting attitudes are shallow and easily reversed. The implication for anyone seeking lasting change, in health and education especially, is that shortcuts buy compliance cheaply while central processing is what makes a new attitude stick.
Examples
A scrutinizing buyer weighs the spec sheet (central); a casual one is swayed by a celebrity endorsement (peripheral).
A leaflet about a rare condition gets skimmed for the logo and the doctor's title; handed to someone just diagnosed, the same leaflet is read line by line.
Voters half-watching a debate while cooking remember who looked confident; those watching closely are still arguing about the tax numbers a week later.
A committee deciding a major capital budget dissects each cost projection line by line; asked to approve routine expense reports, the same members defer to whoever signed off first.
First described in Petty & Cacioppo (1986).
Key references
- Chung, S., & Fink, E. L. (2018). One of the most cited persuasion studies but no success in replication: Investigating replication using Petty, Cacioppo, and Goldman (1981) as an example. Annals of the International Communication Association, 42(1), 1-20. doi.org/10.1080/23808985.2018.1425100
- Luttrell, A., Petty, R. E., & Xu, M. (2017). Replicating and fixing failed replications: The case of need for cognition and argument quality. Journal of Experimental Social Psychology, 69, 178-183. doi.org/10.1016/j.jesp.2016.09.006
- Carpenter, C. J. (2015). A meta-analysis of the ELM's argument quality x processing type predictions. Human Communication Research, 41(4), 501-534. doi.org/10.1111/hcre.12054
- Kruglanski, A. W., & Thompson, E. P. (1999). Persuasion by a single route: A view from the unimodel. Psychological Inquiry, 10(2), 83-109. www.jstor.org/stable/1449223
- Petty, R. E., & Cacioppo, J. T. (1986). The elaboration likelihood model of persuasion. Advances in Experimental Social Psychology, 19, 123-205. doi.org/10.1016/S0065-2601(08)60214-2
- Petty, R. E., Cacioppo, J. T., & Goldman, R. (1981). Personal involvement as a determinant of argument-based persuasion. Journal of Personality and Social Psychology, 41(5), 847-855. doi.org/10.1037/0022-3514.41.5.847