Do you really know your friends?
Do you really know your friends' political beliefs?
Posted Oct 06, 2010
Think of someone you know. It can be anyone, just pick the first person that comes to your mind. How close are you to them? Do you know whether their political beliefs lean more towards conservative or liberal? Do you know how they would answer the question "Do you feel the U.S. spends too much money on assistance to other countries?"
During the 2008 primaries, Sharad Goel, Duncan Watts, and I released a Facebook application that asked questions like these about the users' political beliefs (and some fun, non-political questions like "Would you pay $100 for jeans?") and then let them answer the same question about a randomly chosen friend. If the friend had agreed to share his or her answer, they could see whether they were right or wrong. Most people who played this guessing game enjoyed it, because they could see how well they knew their friends and see how well their friends knew them.
There were 80 unique questions, 47 of which were about politics. We had over 2500 people use the application, who together answered a total of 12,000 questions about their friends. The first thing we found was that, as you would expect, friends are more similar to each other than they are to strangers. On average, people answered the same way as their friends 75% of the time, relative to strangers who answered the same way only 63% of the time This indicates substantial homophily—that is to say, "birds of a feather flock together."
Now, you may notice that 63% agreement is pretty high. This tells us that the people who used our application are more like each other than two people randomly selected from the U.S. To adjust for this, we fit a model that allowed us to answer what we would have gotten if the questions we asked were perfectly divisive; that is, if random strangers only agreed 50% of the time.
However, people thought they were even more similar to each other than they actually were. As you can see in the above figure, the difference between perceived agreement—that is, how often people guessed that their friends would answer the same way they did—and their actual agreement is about 10% on average, with people overestimating their similarity to strong ties by about 7% and to weak ties by about 13%! Thus, although people are fairly similar to their friends, they consistently underestimate how different they can be.
What this means is that people were generally unaware of when their friends disagreed with them! Some might say this is unsurprising, as it is impolite to discuss politics... except that these results hold even for people that said they discussed politics with each other. It is simply that people believe their friends agree with them more than they actually do.
What all of this suggests is that when people are trying to figure out what their friends believe, they tend to rely on what kind of person they are and what they themselves believe, and not very often on real knowledge. This implies that although friends actually have people around them with differing opinions, because of this assumed similarity there seems to be little active discussion that actually has an impact on their beliefs. So now you have to ask yourself: do you really know your friends?
*The work behind this blog post and the figures in it will appear in a forthcoming issue of the Journal of Personality and Social Psychology.