When I canvassed door to door for Barack Obama in 2012, I took a list of registered Democrats and a stack of voter pledge cards. The campaign’s goal was to reach as many Obama supporters as possible and convince them to act. These citizens had a proven record of voting, which meant they should be receptive to our appeals. After confirming their support for President Obama, we asked them to sign the voter pledge card (shown to increase the likelihood of voting) and talk through their plan for getting to the polls.

This “get out the vote” campaign highlights an important truth for social-change advocates: Although it’s common to think persuasion is about changing people’s minds, it’s often more practical to find a friendly audience and get them to act on the beliefs they already have. We didn’t knock on Republican doors, because we didn’t think they’d be receptive. Ingrained attitudes are hard to change.

Receptivity is an important consideration in message design, and it helps determine what type of appeal to use. Will the audience respond best to reasoned arguments or emotional entreaties? Should we invoke self-interest or grab them with gimmicks? (The most-opened emails of Obama’s second campaign simply said “Hey” in the subject line and were ostensibly from the candidate himself, according to the campaign’s email director.)

For nearly a century, social scientists have attempted to unlock the secrets of persuasion. They’ve produced dozens of captivating theories—from classical conditioning to cognitive dissonance. More recently, behavioral economists have written best-sellers (including Thinking, Fast and Slow and Predictably Irrational) that highlight our two modes of decision-making (fast and slow).

Given the richness of the literature, it can be hard for practitioners to know which theory to apply when. That’s where the Elaboration Likelihood Model, or ELM, comes in.

Elaboration Likelihood Model

Social psychologists Richard Petty and John Cacioppo introduced the ELM in 1981 as a meta-theory—a tool to help organize all the other theories. It’s valuable for its ability to bring order to conflicting communication theories. Over the past four decades, it has remained a fixture of persuasion research, subject to controlled studies and meta-analyses that confirm the model’s utility in explaining message processing.

Simply put, the ELM describes how likely it is for an audience to devote careful thought to a message. “Elaboration” refers to the thoughts generated in response to persuasive appeals, which may be either complementary or clashing. “Likelihood” refers to the probability of us doing any thinking at all.

Petty and Cacioppo found that the likelihood of elaboration increases when a message seems personally relevant. For important decisions (like buying a house), we’re more likely to pay attention and try to reason through the information. Such decisions are “high involvement.” But many daily decisions (like which toothpaste to buy) aren’t that important and don’t require careful thought. For these “low involvement” decisions, we’re less likely to elaborate and more likely to be swayed by social cues and mental shortcuts.

“Low involvement” and “high involvement” correspond to the System 1 and System 2 terminology popularized by behavioral economists, who use it to describe our two modes of decision-making. System 1 thinking is characterized by snap judgments based on intuition and association, whereas System 2 involves thoughtful reflection. Knowing an audience’s involvement level is crucial for anticipating the type of thinking they’ll use. Involvement varies by audience, according to their needs and desires. Some people think a lot about toothpaste.

Message Strategy Matrix

I propose a new way of visualizing the ELM that makes it easier to use. The Message Strategy Matrix (see below) helps practitioners segment audiences based on involvement and gives suggestions for persuasive approaches. It has two dimensions. The first is involvement, or how motivated the audience is to think about your message. The second is predisposition, or whether their prior attitude is favorable or unfavorable.

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Predisposition is important, because it’s hard to change people’s minds. Even when communicators are successful in the short term, audiences often revert to their prior attitudes in the long run. And because people tend to seek out information that confirms what they already believe (confirmation bias), predisposition also affects what they hear. This doesn’t mean you should avoid those who strongly disagree. But, with limited resources, it does mean you should pick your battles—and your approach—wisely. The Message Strategy Matrix has four quadrants:

Attentive listeners

These audiences are motivated to pay attention to your message, because it seems important and personally relevant. They’re favorably predisposed—meaning they’re in the market for what you’re offering. Attentive listeners carefully consider facts, evidence, and reasons. Assuming you can make a good case, they should be persuadable. Live audiences are generally attentive listeners if they’ve personally chosen to attend your presentation. A nonprofit’s major donors also land in this category. In public health, attentive listeners are people who have already accepted the need for change and want to know how.

The next two audience quadrants (going clockwise) are “wild cards” owing to their low involvement, which makes them unreliable.

Wild card in favor

These audiences are favorably predisposed but not terribly concerned with the decision—either because it doesn’t seem important or because the question is already settled in their minds. They won’t pay close attention to your message or try to reason through it. But you may be able to trigger them into action with low-involvement cues that spur System 1 thinking (mental shortcuts). Robert Cialdini describes six such cues in his classic book, Influence. Among them are scarcity (emphasizing limited time or availability) and consistency (encouraging people to follow through on commitments, as we did with the voter pledge cards).

Another way to influence wild-card-in-favor audiences is through framing and choice architecture. The idea here is that small changes in the way a choice is presented or framed, can have a big impact on an audience’s behavior (see Richard Thaler and Cass Sunstein’s Nudge). When you visit a restaurant, do you make your decision based on the menu provided, assuming that what you see listed is all there is? If so, whoever created the menu is channeling your choices. The same thing happens with other predetermined options, such as health-insurance packages or charity-giving levels.

Finally, TV advertisers have traditionally focused their appeals on wild-card-in-favor audiences, trying to build emotional associations (another low-involvement cue) so that customers will remember their products at point of sale. Commercials making use of celebrity spokespeople and cuddly cartoons fall into this category. Also, audiences in this quadrant may choose your product or service out of convenience, which makes timing and placement important.

Wild card against

These audiences are like the “wild card in favors,” except they default to the opposing side. You can try mental shortcuts, framing, and choice architecture. Direct experience (sampling) can also work. For years I avoided Brussels sprouts. That was my default position, and I didn’t give it much thought. One night a friend placed some on my dinner plate. I tried them and found they weren’t so bad! Direct experience changed my attitude, taking me from low-involvement naysayer to attentive listener.

Tough crowd

Motivated opponents are the hardest to persuade. If you make a good argument, they come back with counter-arguments. If you present facts, they respond with alternative facts. When values are involved, it’s even harder to get people to budge (consider abortion rights and gun control). Persuasion attempts often boomerang, making tough crowds the least cost-effective to work with, but attitudes can change over time.

Appealing to tough crowds means carefully selecting your starting point to avoid immediate rejection. You can choose a spokesperson they trust, focus on shared values, or create opportunities for cooperative learning (bringing people together to work toward a common goal). Or you can tell a good story. Researchers have found that audiences are less likely to counter-argue messages embedded in stories, because the fictionalized accounts seem less threatening (see Melanie Green, Jeffrey Strange, and Timothy Brock’s Narrative Impact). Examples include Uncle Tom’s Cabin, which advanced the Abolition movement, and the feature film Boys Don’t Cry, which spurred new legislation against hate crimes.

The persuadable audience

Today, marketing agencies have sophisticated tools for assessing audience attitudes and tracking behavioral patterns online. But social-change advocates don’t always have access to these tools. Even when they do, they must still select the right lever to apply. The Message Strategy Matrix can help by segmenting audiences according to involvement and suggesting possible approaches. It lets practitioners locate the persuadable audience.

This is what the Obama campaign aimed to do with its canvassing strategy. We had neither the time nor the resources to visit tough crowd households. Instead, we focused on the favorably predisposed registered Democrats. We engaged attentive listeners in conversation. We gained commitment from wild-card-in-favor voters using triggering techniques.

The result? People listened.