Homophily changes the way we think

You think for yourself, but act like your friends

Birds of a feather tend to shop together.  That we know.  They also tend to talk together and walk together; and who their friends are affects more than just what type of jeans they buy.  Their friends have the capacity to affect their tastes, activities, and their lives overall.  Sociologists call this phenomenon of being affected by one's friends "homophily" - the tendency to associate with people similar to you and the people you associate with tend to act like you over time (and vice-versa).   

Humans naturally conform to social influence - to their surroundings, environment, strangers, peers, friends, and the like.  People tend to socially conform or mimic their friends' behaviors, attitudes, etc.  Besides the need for information, it is understood that people conform so that they will be liked and accepted by other people. 

We tend to associate ourselves with those who are similar to us in interests, attitudes, values, background, and personality.  The old saying that "opposites attract" doesn't hold much weight; research evidence by Miller McPherson shows that it is similarity that draws people together (imagine starting with another female from San Francisco El Alto, 21, GT on social networks like Flickr/LinkedIn/Plaxo/Facebook you). 

The Effect Your Friends Have Over You

Your peers are very important.  Judith Rich Harris's groundbreaking book, The Nurture Assumption, suggests that peers have a much greater influence on child development than parents or teachers.  An immigrant 4-year-old boy from Poland (or China) who just moved to St. Louis is more likely to speak perfect English and love baseball within a year because he wants to fit in with the other kids.  He might still like traditional Polish food, but he'll also quickly love hamburgers and pizza.      

The social psychology phenomenon of "mirroring" - people that are your friends or people that like you in general, tend to physically mimic or mirror your behavior, vernacular, movements, etc. - is example of the type of subconscious influence your friends have over you.  As a social experiment, try incorporating a new word or phrase into your lexicon and notice how your friends will slowly adopt and use this word or phrase.  Or try crossing your arms during a conversation with one of your friends and see if they mimic that behavior.

On a gender basis, women are slightly more prone to be influenced by their female friends than men are by their male friends.  In her research Sex Differences in Social Behavior, Alice Eagly hypothesizes that this stems from the social roles men and women are taught in our society.

How Your Friends Affect Your ...

- Music Preferences
 
Birds of feather even sing together.  Noah Mark, Assistant Professor at UNC Charlotte, wrote a paper in 1998 that suggests that our music preferences are highly influenced by who we hang out with.  This makes complete sense.  We are limited in our time and capacity to try everything.  So we tend to try out and learn about things that our friends are doing, acting as a filter to all the noise that permeates our ear drums.  I suspect this is also true with the type of sports you play, art you like, food you appreciate, etc. - all your habits, likes, and dislikes are massively influenced by your friends' habits.  

 
Political leanings is very closely linked to homophily.  If you live in an area with more than 65% party registration, you're probably getting massively influenced by your neighbors. 
 
Using the Understanding of Homophily for Good Use
 
Homophily can be actively used to positively impact your life.  Christakis and Fowler did another study where they found quitting smoking is contagious and targeted interventions are most successful when done within a group.  It's analogous to going for a run with a friend and pushing yourself harder and longer than if you were to just run by yourself.  Having many people around you can reinforce positive things like community service or negative things like UFO cults.   

If you are always trying to hack your life, the best thing you can do is systematically eliminate unhappy people from your encounters.  Even a reduction of 10% unhappy people will likely have dramatic affects on your mood and disposition.  Good-bye complainers, hello smilers.

The best way to deal with homophily is to understand how you are impacted by it and to hack your life and make adjustments accordingly.  To inoculate yourself politically, for instance, start considering the "other side" of the political isle.  If you are in San Francisco (84% Democratic), you might want to read the Wall Street Journal editorials every day.  Similarly, if you are in the back countries of Alabama (70% Republican) you should read the editorials of the New York Times every day.  Don't let yourself be blindly led by those you know.  

So the next time you go shopping, be sure to bring along that frugal friend of yours to help curtail your spending spree - which is definitely not recommended in this economy.
 
(A special thanks to Vivek Sodera for his edits and research)