How many arguments make you most persuasive?

When trying to persuade someone, should you share every argument you can think of, or just some?

Most people figure that the more reasons they give someone to say yes, the more likely they are to.

After all, if we were trying to bribe them to say yes with candy, the more candy we offered, the more eager they’d be to accept. Right?

Actually, it turns out that it’s not that simple.

The chocolate analogy.

Let’s say that you and Lisa are having a disagreement and both of you decide to try to bribe Paul to take your side, using his biggest weakness: chocolate.

Logic tells us that if you’re able to offer more chocolate in your bribe than Lisa does to hers, odds are that Paul will side with you.

But what if the two of you are equally matched on your chocolate supply?

In that case, you might be tempted to throw a few packets of raisins into the mix to try to tip the scale. Because more is better, right?

Well, only if Paul likes raisins.

If he doesn’t, adding them to your bribe can actually make it seem less attractive to him than Lisa’s bribe, even though the amount of chocolate is the same.

After all, when Paul looks at Lisa’s pile, he only sees things he likes. But when he looks at yours, he sees things he likes mixed with things he doesn’t.

Now, swap “chocolate” for “strong arguments” and “raisins” for “weak arguments”.

Arguments are averaged, not summed.

In a 2024 study, researchers conducted four experiments to test whether including additional arguments alongside a strong one helps or hurts persuasion.

They had people read persuasive texts with either only one strong argument, only weak arguments, or a mix of one strong and several less-strong arguments, and then rate how persuasive the texts were.

That texts with only weak arguments were the least convincing was unsurprising. But it also turned out that when weak arguments were combined with a strong one, the text became less convincing than if the strong argument was presented on its own.

And the winner? Texts with one strong and one or more moderately strong arguments.

The scientists concluded that when we weigh arguments for something, we don’t sum them up in a way that makes every argument add points. We average the arguments into a single “persuasion score”.

In other words, our arguments are rated in much the same way as we rate products online.

Studies show that products that have nearly 5 stars actually perform better than products with a perfect 5*, so a few 4-star reviews along with the 5-star ones actually make a product more attractive to buyers. But if a product has a lot of 1- and 2-star reviews, our trust in its quality quickly drops.

*Perfect 5-star reviews tend to make people suspicious of whether the reviews are trustworthy or not.

Focused arguments are more persuasive.

So if we want to be more persuasive, a good strategy is to practice scoring our arguments before we present them.

Whenever you’re preparing to persuade someone, take some time to rate your arguments on a 1 to 5 scale. Then, during the conversation, focus only on the arguments that scored 4 or 5, and use the 1-3 arguments only as Hail Marys if you still get a no after presenting your best ones.

Practicing this when you have the chance to prepare will also make it a lot easier to do the ratings on the fly, whenever spontaneous persuasion situations come up.

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Study: Obermaier, M., Koch, T. The paradox of argument strength: how weak arguments undermine the persuasive effects of strong arguments. Sci Rep 14, 22244 (2024). https://doi.org/10.1038/s41598-024-73348-1