It seems to me that people who are obese seem to spend lots of time around with other people who are obese. Smokers tend to pal around with other smokers. This raises an important question: Do friends cause each other to pick up bad habits? Not that I’m claiming it to be intentional, but do people pass bad habits to their friends through some form of social osmosis? Allow me to begin with a story that embarrasses me. When I was 18, I met a guy named “Ray” who was smart, funny and an accomplished athlete. Ray also had a noticeable tic . He sporadically jerked his head whenever he talked with others—he did this several times per minute. I spent some time with Ray while visiting my then-girlfriend at college back in the 70's. After a few days up at her college, I noticed that I was starting to exhibit the same tic. I can assure you that I didn’t do this intentionally. When I noticed the problem I consciously forced myself to stop doing it, lest it became an ingrained habit. Did Ray’s bad habit cause me to pick up my new bad habit? Based on the timing, there’s not much doubt in my mind. Similarly, I’ve noticed that when I like someone and I’ve spent considerable time with them, I sometimes start talking like them, picking up their dialect, their expressions, their gestures and their vocabulary; the clues are usually subtle but often undeniable. I’ve caught myself doing this dozens of times over my life.