How Other People Influence Your Eating

So, you're at a barbecue. You already had a hamburger, a lump of potato salad, and plenty of carrots smothered in ranch sauce. Yet, even after that, you're still hungry. Do you go up for a second round? Or do you just head over to the snack section and just load up on pretzels?

More often than not, the answer is you'll look around, see what everyone else is doing, and follow suit. This is the concept of "social modeling," and it has an extraordinary effect on how we eat.

Dr. Lenny Vartanian, an associate professor at the University of New South Wales in Australia, led an analysis of 38 studies looking at how the phenomenon dictates our eating methods. The results are fascinating. I spoke with Vartanian over Skype and we delved into them.


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So, how do other people affect how we eat?

Dr. Lenny Vartanian: There are a few different social influences. One of them is what we would call social facilitation, the general idea that when you're in larger groups you tend to eat more. There's another version of it as impression management, so we eat in different ways because we want to convey a particular impression to someone else. If I'm on a date and I want to seem very masculine, I'm not going to order the quiche, I'll order the steak. That kind of idea. What we're looking at is this effect called modeling, which is that I'll shift how much I eat in accordance to how much you're eating.

How large of a difference in consumption is due to these effects?

Vartanian: The effect we're getting for modeling food intake is about twice the amount of the statistical effect you get for portion size. If you double the portion that people get, they'll eat this much more, and that effect is a certain magnitude. So, the modeling effect is twice that size. Studies show that even if you've been deprived for 24 hours, and you're sitting across from someone not eating much, you won't eat as much either. Our social cues actually override our internal signal of hunger.

Why do social cues have such an effect?

Vartanian: I think it has to do with the fact that in many places, the right thing to do is not really clear. If you go to an All You Can Eat buffet, how many times is it appropriate to get more? Are we supposed to eat until we can't move? In those situations there is ambiguity, and where there's ambiguity, we rely on cues from the outside world.

If everyone is patterning their eating behavior off everyone else, what about the first person making the decision to eat more? Is there some kind of leader in social situations?

Vartanian: There have been two kinds of studies. In one they have a confederate. That confederate's been instructed to eat a large amount or small amount, and we can look experimentally at that to see how it influences the participant. The other collection of studies is two participants -- watching TV or having a conversation -- and just look at how much people eat. Nobody has been instructed to limit their food intake, it's just a natural process. What we see in those studies is that the effect is stronger. The correspondence is stronger than in the experimental studies. I influence you, and you influence me, and this back and forth and give and take until we level out. But who ends up being the leader is not really clear. We just don't know that.

That said, we don't just follow people blindly. If you're a lean person and you're modeling the behavior of someone who is obese, you still eat more if they eat more, or less if they eat less, but the extent of which you follow them is not as much as if it was a lean person you were following. So you do a mental calculation: I can eat more because that person is obese, but I can't eat that much. There is some mental gymnastics about trying to figure out what the best course of action is.

How can we use this study?

Vartanian: We can also use this as a way to eat healthier overall. We know that in the U.S. and Canada and Australia, people don't eat enough vegetables. Very few people hit the target. So if we can use these social norms to encourage fruit and vegetable consumption, that would be a way to use these norms for good. Putting up some advertisements or posters or things that would hint at what the norm is. We see that with alcohol consumption, that there are advertising campaigns and public service announcements that try to change perspectives about what's normal. It's adopting that into the food world.

Also, I don't think there's anything inherently wrong in following other people in how they're eating, especially since the research shows that the pattern is people eat less when other people eat less rather than the opposite.

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