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How Many Arguments Are Enough to Be Persuasive?

Imagine two people try to convince you to buy their respective brands of kitchen products. The first representative gives you 10 reasons to buy her brand and the second representative only gives you 1 reason. So far, the first person seems more persuasive. After all, aren’t 10 reasons better than 1?

But what if the first person gives 5 compelling reasons to buy her brand and the other 5 reasons are obviously filler? What if all 10 reasons are silly and the second representative’s only argument is actually really compelling?

Clearly, the question of “quality vs. quantity” in the persuasion game gets complicated fast. Luckily, psychological research gives us insight into how persuaded people are by long and short messages that are strong or weak.

“Strength in Length”: Are More Arguments Always Better?

One early study presented people with a simulated court trial. The participants in the study pretended to be jurors in the case, and they listened to the arguments from the prosecution and the defense. The materials were set up so that one side had more arguments than the other. Specifically, one side would give one argument and the other would give seven. Not surprisingly, in this scenario, participants’ verdicts came down on whichever side provided more arguments.

One question researchers have asked, though, is: do more arguments make a more persuasive message even when those arguments are weak? In other words, it makes sense that 10 compelling arguments would be more persuasive than only 1 compelling argument, but it’s not clear whether having 10 really stupid arguments is any more persuasive than having just 1 stupid argument.

More Reasons Produce More Persuasion When People Aren’t Thinking Much

You can think of the “Longer is Stronger” rule as a trick people can use when they don’t want to actually read or listen to the whole message. It turns out that having more reasons is still more persuasive, even if those reasons aren’t any good, when people aren’t paying close attention to the message, As Richard Petty and John Cacioppo wrote:

If people are unmotivated or are unable to think about the message…they might invoke the simple but reasonable decision rule, “the more arguments the better.”

hand-859521_640To test whether people really do this, one study gave people an essay containing either three reasons to adopt a new policy or nine reasons to do so. For some people, all of the reasons provided in the essay were strong, compelling reasons, but for everyone else, all of the reasons were really weak.

For people who didn’t care about the policy (so they weren’t too interested in dissecting the arguments), they were more persuaded when they saw nine reasons than when they saw three. It didn’t even matter whether those reasons were strong or weak.

Another study showed similar results. When people weren’t really paying close attention to an article, they changed their opinions more if the article was relatively long, compared to when it was shorter. Once again, the quality of the article didn’t matter—just the length.

What About When People Are Thinking?

Okay, so you have a captive audience, and they’re willing to think deeply about your persuasive arguments. Should you still strive to craft a lot of arguments regardless of their quality?

hand-859523_640Under these circumstances, the research suggests that you should make sure your arguments are good first and then worry about how many you have. In the two studies I mentioned above, when the conditions were flipped and people were in a position to really read and consider the persuasive essays, they were more persuaded when the essays had strong arguments than when they had weak ones.

It’s possible, though, that having more good arguments can still be better than having only a few good arguments. In other words, if you know people are paying attention, you may not want to completely disregard the length of your message. In both studies, there’s a tendency for messages with many compelling arguments to outperform those with only a few compelling arguments (when people are paying attention).[1]I’m avoiding making strong claims here because the statistics for these results are weaker than for the other ones. Based on my reading of these studies, I wouldn’t make too much of this pattern, but the pattern does seem to be there.

When Longer Messages Can Backfire

Overall, it seems like it wouldn’t hurt to just make sure you have longer messages. It’ll appeal to people who aren’t paying close attention, and it can still be impressive to people who are paying attention.

Still, you need to consider the inherent strength of the claims you’re making. There’s a trend in one of the studies I’ve reviewed here where having more arguments can produce less persuasion. This is the case when (a) all of the arguments are actually weak and (b) the audience feels compelled to really process what the person has to say. You can imagine someone in this position thinking, “Wow–these aren’t persuasive at all…and there are so many of them!”[2]It reminds me, if only tangentially, of the joke in Annie Hall: “There’s an old joke… two elderly women are at a Catskill mountain resort, and one of them says, “Boy, the food at this place is really terrible.” The other one says, “Yeah, I know; and such small portions.” Well, that’s essentially how I feel about life – full of loneliness, and misery, and suffering, and unhappiness, and it’s all over much too quickly.”

Also, other research has shown that adding weak arguments to strong arguments can water down the impact of a persuasive message. Even though a message with nine compelling reasons is better than one with just three, adding weak reasons to a message that has nine compelling ones reduces its persuasiveness.

Finally, some have suggested that messages can lose their impact if they get too long, regardless of how good its points are. If a message drags on, people can tune out, especially if the arguments become really repetitive.

Was This Article Long Enough For You?

So, as with most things, the answer to the question “Is it more persuasive to have a lot of arguments?” is: “it depends.”

When you have a lot of “objectively” persuasive reasons that you can give people, then it seems like it’s better to present all of them[3]As long as you don’t repeat them over and over, as mentioned earlier. For people who aren’t ready to invest the time it takes to process your message, the sheer number of arguments will be persuasive. For people who are ready to think about your message, the quality (and number) will be persuasive.

If you know that you don’t have too many compelling arguments in your arsenal, then you need to think about how closely people will be paying attention. If you know that your audience isn’t likely to give your message too much thought, then pile on the vacuous arguments! If your message will be held to scrutiny, then stick with your more compelling arguments, even if there are only a few.

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Footnotes   [ + ]

1. I’m avoiding making strong claims here because the statistics for these results are weaker than for the other ones. Based on my reading of these studies, I wouldn’t make too much of this pattern, but the pattern does seem to be there.
2. It reminds me, if only tangentially, of the joke in Annie Hall: “There’s an old joke… two elderly women are at a Catskill mountain resort, and one of them says, “Boy, the food at this place is really terrible.” The other one says, “Yeah, I know; and such small portions.” Well, that’s essentially how I feel about life – full of loneliness, and misery, and suffering, and unhappiness, and it’s all over much too quickly.”
3. As long as you don’t repeat them over and over, as mentioned earlier.

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