The fourth principle of making ideas stick is making messages credible. Will people believe what you have to say? And usually, when we think about getting people to believe our message, our default tendency is to use statistics. We think if we use a lot of statistics, a lot of numbers, people will believe us. And numbers can be useful. They can be useful in convincing people. But often, numbers aren't very memorable. When people hear numbers they say oh, that's a good point, but later on they can't remember what you said. And so if your goal is not just to be convincing when you're in the room, but make sure people remember what you say when you leave the room, you need to make sure you're getting credibility beyond just the statistics we're using. How can, if we're gonna use statistics, can we put them in context to make them more impactful? How can we make sure your ideas will stay behind even after you've left the room? Imagine, for example, you're going in for a job interview and you want people to remember you. Not just how much they liked you when you were sitting in the room, but after they've sat through ten other candidates beyond you, are they gonna remember the conversation they had with you? How can by making yourself more credible, you be more memorable? So let's use a different example to understand that idea of credibility. Say you wanna convince people that the state of California needs more tax dollars, so to do that you want them to see that California is a really big place. So you might use statistics. You might say the state of California has 33 million people. It's quite large. Someone listening to that message might say, so what? I have some sense of how 33 million is. It's bigger than 30 million and smaller than 35, but I don't really know how big that number is. I don't have a visceral sense of it's large rather than small. What if instead of saying California has 33 million people, I told you that California has more people than Alaska, Arkansas, Delaware, Hawaii, Idaho, Iowa, Kansas, Maine, Mississippi, Montana, Nebraska, Nevada, New Hampshire, New Mexico, North Dakota, Oregon, Rhode Island, South Dakota, Utah, Vermont, West Virginia, and Wyoming combined. Now how big is California? Well, if you have any idea how big those states are, you're probably going, wow, if it's as big as all those states together it must be quite large. What that does is by putting it in comparison to other things we know and understand, it gives us a reference point to know how big it is. Just like that example with the Apple computer coming out of an envelope. Apple didn't say we make very thin computers. They showed us comparing it to something we all know and understand. We all know that an envelope is thin, so if it fit in an envelope it must be quite small. We wanna give numbers some context. Let me give you one more example of this. Imagine you wanna convince people that movie popcorn has a lot of fat. You want them to realize that it often has 37 grams of fat in it. Well, you could say that a movie-size popcorn has 37 grams of fat. And someone would sit there going, okay, that's more than 30 and less than 40. But most of us don't have a good sense of how many grams of fat we're supposed to have on a daily basis. So you don't know if 37 is large or small. What if instead I said a medium-size butter popcorn at a typical neighborhood movie theater contains more fat than a bacon-and-egg breakfast, a Big Mac and fries for lunch, and a steak dinner with all the trimmings combined? Well, now you have a really good sense of how much fat in it. How much fat is there in movie popcorn? There's a whole lot of fat in movie popcorn. If I said movie popcorn has as much fat as two sticks of butter, you probably wouldn't wanna eat it anymore. And so in trying to convince people of your ideas, to get them to adopt our messages, if we're gonna use statistics, make sure to put those numbers in context. And one way to do that effectively is a principle called testable credentials. And the idea here simply is to make people convince themselves. There is an old ad that did this job very effectively. They were selling a hair coloring product and they wanted to convince people that that product would make them look years younger. Now again, they could tell people our product will make you look years younger, til they're blue in the face. But how could they convince people? How could they get people to convince themselves that the product was good? Well, what they did was they made an ad with a gentleman in two halves and they asked people to put their hand over one half, the gray half, and see how much younger I look. Half the gentleman's hair was gray, and half the gentleman's hair was black after having used the product. Well, if you try that exercise, if you put your hand over the gray half, you might say wow, the guy looks maybe 35 or 40. And if you put your hand on the half with the darker hair and look at the gray half, you might say well, he looks maybe 65 or 70. What you've done by engaging in that exercise is you've convinced yourself that the product is effective. You've seen, wow, using this makes this guy look younger, it must be quite effective. The brand Clinique has done the same thing with a tape test they have. They ask you to take the brand, put some moisturizer onto one of your hands, and put a piece of tape on that hand, as well as the other hand without moisturizer. And then by looking at the tape, you can see how many skin cells came off over one versus the other. By comparing the two, by getting people to do the work themselves they gave testable credentials to individuals. Rather than trying to convince the people, hey, our message is good, they encourage the consumers or individuals to do it themselves.