This blog entry by Tyler Cowen reminded me of the course that Seth Roberts and I once taught on left-handedness. The main things I remember learning:
1. Left-handedness is not the opposite of right-handedness. Most righties do everything with their right hand, but lefties are mostly mixed. Also, left-handers are typically OK with their right hands, but righties are typically not so good the other way. Related to this is that there’s really not such a thing as “ambidextrous”: the term “mixed-handed” is better: people who use different hands for different tasks are usually OK with either hand.
2. This is more of a “folk psychology” thing, but it’s interesting: a lot of people, especially lefties, either want to know the “rule” for determining whether someone is left-handed, or think there is such a rule. Many people aren’t comfortable with the idea of a continuum, and want this to be a binary variable. (Interestingly, I even ran across a statistics textbook once that (mistakenly) characterized handedness as an example of a categorical variable.)
3. The studies that find lefties to die younger are interesting. Not airtight, but not trivially demolishable, either. At least as of my reading in 1994, the case is still open on this one.
4. We did a little study in our class (approx 20 students, about 1/4 righties and the rest left- or mixed-handed), asking each student to make a list of his or her closest friends (outside of the class itself) and then give them the handedness inventory (a standard 10-question battery that yields a handedness score between -1 and 1). We found a statistically significant correlation between the handedness of the people in the class and the average handedness scores of their friends. We never followed this up with further studies, though.
5. In reading the papers for the class, I noticed that many were written by scientists from Canada and New Zealand, not much from the U.S. I asked Seth why, and he said it’s because you can study handedness with a low budget.
6. We were featured in the local papers as an example of a fun college class. But there was one media outlet that contacted us, I don’t remember which one, which Seth suspected was trying to use us as an example of the crap that gets taught in college nowadays. I was careful to be very boring when talking with this reporter so that he wouldn’t get any incriminating quotes from me. Also, a local TV station wanted to come and shoot one of our classes, but they decided not to when I explained that we weren’t really focusing on original research–the course was mostly discussions of existing articles. (It was a good class, though, I think.)