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How to Make Your Arguments Stronger (Hint: Longer Is Not the Answer)

Resist the temptation to bury people under a blizzard of evidence, says psychology researcher Niro Sivanathan. He explains why.

TED Ideas
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Illustration by Monica Garwood.

Have you ever been in a heated discussion (Breaking Bad vs. The Wire; spring vs. fall; small college vs. large university; carbon offsets vs. renewable energy credits) and wanted so badly to show the other person just how wrong they were? If you’re like most of us, you tried to overwhelm your opponent with sheer quantity, to barrage them with every scrap of evidence you could think up.

As it turns out, piling on the proof is an unwise approach, says Niro Sivanathan, a psychology researcher and associate professor of organizational behavior at London Business School in a TEDxLondonBusinessSchool talk. That’s because when we double down on our arguments, we’re setting ourselves up to be undone by the so-called “dilution effect”.

For humans, receiving too much information interferes with our ability to process it. Sivanathan explain that our minds deal with this by quickly sorting the input received into two types: diagnostic and non-diagnostic. He says, “Diagnostic information is information of relevance to the evaluation being made; non-diagnostic is information that is irrelevant or inconsequential to that evaluation. When both categories of information are mixed, dilution occurs.”

To show you how this works, Sivanathan describes two different students: Tim and Tom.

Tim studies 31 hours a week outside class.

Tom also studies 31 hours a week outside class. He has a brother and two sisters, he visits his grandparents, he once went on a blind date, and he plays pool every two months.

In an experiment, says Sivanathan, most of the participants said that Tim had a significantly higher GPA than Tom — even though the two put in the exact same amount of time studying. Why? All of the non-diagnostic information (the extraneous detail about his personal life) given about Tom diluted the diagnostic information (how many hours he studies) presented.

“The most robust psychological explanation for this is averaging,” says Sivanathan. Rather than adding up pieces of information and assigning them different values, most of us appear to average them in their minds. He adds, “So when you introduce irrelevant or even weak arguments, those weak arguments reduce the weight of your overall argument.”

One example of how this dilution effect has real-world consequences is in drug advertising, says Sivanathan. It’s requirement in the US for the side effects of prescription medications must be listed at the end of TV or radio commercials. But if you listen, you’ll notice that the commercials never end right after the listing of the major side effects such as stroke, heart attack or death. Instead, they’ll either end on minor side effects (such as headaches or itchiness) or on neutral information (such as telling people to discuss medication with their doctor). The drug manufacturers, consciously or not, is using the dilution effect — by including so much information, they end up watering down consumers’ assessments of how risky the drug actually is.

Sivanathan found this phenomenon confirmed in his own research. In one study, two groups of people were shown lists of side effects for the same drug. One group’s list contained both major and minor side effects, while the other group’s list contained just the major side effects. The results: “Individuals who were exposed to both the major side effects as well as the minor side effects rated the drug’s overall severity to be significantly lower than those who were only exposed to the major side effects,” says Sivanathan. “Furthermore, they also showed greater attraction towards consuming this drug.”

How can you use his insights to win over people in your own life? Sivanathan advises us to stick to their strongest points; resist the temptation to try besting others with brute force. “The next time you want to speak up in a meeting, speak in favor of a government legislation that you’re deeply passionate about, or help a friend see the world through a different lens, it’s important to note that the delivery of your message is every bit as important as its content,” he says. “You cannot increase the quality of an argument by simply increasing the quantity of your argument.”

Watch his TEDxLondonBusinessSchool talk now:

Niro Savanthan Niro Sivanathan is an associate professor of organizational behavior at London Business School. His research explores how the psychology of the self – specifically our motivation to maintain the integrity of the self – influences our decision making.