How To Become a Dancefloor Dandy
William - We found that the quality of an individual's dance is related to their bodily symmetry and this effect is much stronger in men than it is in women.
Chris - How did you actually make these measurements? What did you do?
William - Well we used digital callipers, which is quite standard in terms of measuring very small deviations from perfect symmetry in bilateral traits like our ears, our ankles and our knees. We did this twice over two periods of time: in 1996 and 2002. This is to control for any type of measurement error or compensatory growth changes in symmetry over time. We selected individuals who were symmetrical over both time periods and then also individuals who were asymmetric across both time periods. We brought the into the lab in Jamaica and had them dance to a very popular song in their culture in Jamaica.
Chris - Disco lights added?
William - We didn't have disco lights, but what we did have were eight motion capture cameras. These are high speed cameras that emitted infra red beams to 41 reflectors on each dancer's body.
Chris - This so you can map out exactly what moves they're making?
William - We can mathematically map out all the movements that they were making. We can capture the movement and separate it from the actual person. The reason we wanted to do that is that one problem if we have this hypothesis that your mate quality or your symmetry is related to your dance quality, how do we assess dance quality? This can be challenging because maybe people's assessment of dance quality could be biased by how you look. These include the clothes you're wearing, your facial attractiveness, or whatever it may be. By using motion capture high speed cameras we could separate that from the dancer and through computers put that onto a standardised animated figure. We then presented those figures to a group of perceivers.
Chris - And the people you asked to judge and give marks out of ten; were they a mixture of men and women?
William - These are a mixture of men and women from the same population in Jamaica.
Chris - What was the finding?
William - The first finding was that they preferred the dances by symmetrical males more so than asymmetrical males.
Chris - And where are you going to go next with this? Are you going to try different types of music?
William - We'd like to test different types of music and perhaps different cultures to see how much we can generalised this effect. But one of the other things we need to do is to see exactly what specific movements are associated with symmetry. Since we've mathematically captured the movements on motion capture we can analyse specific, for example, trunk movements, which is something I'm analysing right now. I also want to do follow up studies over time to see whether or not dance ability in any way correlates with reproductive fitness or success.
Chris - It would also be quite interesting to try and teach the ingredients if a good dance to someone who started off as a really bad dancer.
William - Yes it would. To be honest, when I do actually look at the mathematical movements of the dancers in Jamaica, I do spend some time trying to imitate them and seeing whether or not I can improve my own dance ability. I must admit though, the trunk movements are especially hard to imitate.