Meet People photo from ShutterstockLooking to persuade someone that you’re the absolute right person for a job or a new business? Turns out that how much you say about yourself might matter more than what you say about yourself.

When we’re trying to convince someone that a person or a product is great, the tendency is to keep telling them positive things (aka “claims”) until they get as enthusiastic about it as we are. It’s human instinct – everyone does it from experienced marketers down to people just starting out. But that’s the wrong approach.

Research shows that people react negatively when too many good points are thrown at them at once. In a famous Columbia University study (pdf), researchers set-up a sampling booth with different varieties of jam. Customers were invited to find out the perfect jam for them – and the results were surprising.

When the researchers laid out 6 varieties of jam, only 40% of the people who came in the store stopped for samples. When they put out 24 different varieties of jam, 60% of the customers walking into the store stopped by for a taste. So obviously that means that more is better, right?

Not true. Even though fewer customers tried jam when there were only 6 varieties to sample, 30% of those customers bought a jar of jam. Of the customers who stopped to try the 24 varieties, only 3% purchased!

That means, if 1000 people came into the store during each experiment, 120 bought jam when there were only 6 samples on the table, while only 18 customers bought jam when there were 24 samples on the table! That’s a BIG difference!

But wait, you’re probably thinking. I’m not a product, I’m a person.

That’s true, and there’s even long-standing research from the 1960s to support that the more positive things you say about someone, the better the impression people will have about that person.

Except this doesn’t apply when you’re trying to convince someone else. Many other studies show that when people know they are being sold to, they begin “coping” (pdf) by disengaging, ignoring the message or simply discounting it altogether. So when you are applying for a job or becoming an entrepreneur, you need to think like a marketer selling a “product” when you develop your “claims” about why someone needs you.

That is why the jam tasting appeared suspicious to people. Customers were enthused to try so many varieties, but they probably ended up thinking, “the jam makers must not be very good at making jam if they need to make 24 varieties in order to create one I’ll like.”

So what is the magic number? Three.

People tend to believe that they can form impressions about people and products after only 3 impressions. This phenomenon plays out across society. In baseball, players only get three chances to swing at the ball. In tossing a coin or Rock, Paper, Scissors, three tries is enough to determine the winner. Even book series are usually trilogies.

In a fascinating article published in January 2014 in the Journal of Marketing (pdf), researchers tested how many positive “claims” should be made about a product in a series of experiments. They found that when a person is told up to 3 positive traits about a product, they viewed that product more favorably. However, as soon as a 4th positive trait appeared, the person started feeling “sold to” and started to view the product more negatively. This result remained consistent across all four trials.

So, when you’re working on your personal brand, don’t let yourself get caught up in listing everything positive about yourself. Remember, that when you’re trying to persuade, giving people more options actually causes them to be less likely to take action – and that if you tell someone more than three positive things about yourself, your listener will begin to suspect an ulterior motive and believe that you’re trying too hard.