[Voiceover] Let's say that this is you and that these are your friends. What kind of things are you most likely to have in common with these friends? Well, it turns out just about everything, and that's because similarity or how similar someone is to us is a huge predictor of attraction. Compared to any two random
people that you might find, close friends and couples
are far more likely to share common attitudes,
beliefs, and interests, and it doesn't stop there. We tend to befriend and
partner up with people who match our age and race and religion, even things like economic
status and educational level. We like people who are like ourselves, and this has been demonstrated
through a number of surveys and correlational studies, but
it's also been demonstrated experimentally as well. In one study, university
students were brought into a lab, and they were told that
they were going to be playing a game with another student. In reality, the other
student was a confederate, meaning that they were in
on the study the whole time. Participants were split
into one of two conditions. In one condition, they were shown the image of the other player,
in this case our confederate. In the second condition,
participants also saw a picture of the other player, but unbeknownst to them, that picture had some of their own facial
features mapped onto it, and the results of this study showed that the individual was much more likely to cooperate with the other player and to deem them as trustworthy when the picture of the other
player had some of their own facial features morphed into it. Other studies have shown similar findings. We're more likely to think
that another individual is attractive when their facial features are morphed with our own. We're even more likely to
vote for political candidates whose photographs have been changed to include some of our facial features. So, when I say that we like
people who are like us, I don't just mean that in terms
of attitudes and interests. We are more likely to like
people who are similar to us on any level, even if they just share some of our facial features. So, we've noted that similarity can help to bring people together, but does it help them stay together? Do friendships and relationships
tend to last longer the more similar we are? And the research has shown
that the answer is yes, but it's a little bit complicated, because I think it would
be really easy to say that couples who are really
similar to each other share a lot of attitudes and
share a lot of interests. And it seems fairly obvious
how those shared interests could keep two people together
over long periods of time, but it could also be the case
that couples stay together because of perceptions of similarity. and this could mean one of two things. The first is that as couples stay together and share their interests with each other, their interests tend to
become more aligned over time. So, it's not that couples who
stay together for a long time are similar in general. More like they become
similar as time goes on. Another option would be
that perceived similarity could be just that, perceived. Maybe individuals who stay
together for long periods of time merely think that the other
person is similar to them. After all, the way that
this data is collected is typically through surveys. So, it could be that
couples who stay together for long periods of time aren't actually that similar at all, they just think that they are. The thing I find to be most interesting about the similarity effect
is what it might leave out. Because it's not really hard to see how the similarity effect could actually become a similarity bias, because while on the one hand it predicts that we will like people who are like us, it also kind of implies
that we will not befriend people who are different from us. So, the same force that
helps pull people together, might cause them to exclude individuals who are physically or culturally
different from themselves.