How Do I Influence the Health of Other People in My Social Network?

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Absolutely, absolutely, and in fact the interesting thing about this is this can happen even if the person who connects the two of you doesn't change themselves. So the easiest thing to demonstrate is that your friend's friend, someone that you don't know, but someone that your friend knows.

If your friend's friend changes their behaviour, that might change your friend's behaviour, and then the change in your friend then causes you to change. So your friend's friend might start jogging and then your friend might start jogging and then you might start jogging. So you have this ripples that can spread and you didn't know the original person that started this cascade.

But even more amazingly, you might have a friend's friend who goes on a diet, and your friend already is at a weight they are happy with, and so they don't go on a diet, but they're really pleased with their friends progress, and in the course of everyday conversation, they talk to you and say, oh, did you hear about this new diet my friend is having a lot of success with it? And you say to yourself gee, that sounds like a really interesting idea and then you try it as well.

So you friend's friend changed and you change even though your friend didn't change, your friend acted as a carrier of the disease if you will, and so this is one of the things that we found evidence for in this research studies. It's surprising how strong a relationship is between friend's of friend's and friend's of friend's of friend's.

It strong enough that the only way you could explain the strength of those relationships is if you had this sort of carrier status going on in the years between you and those other people.