Tuesday, September 10, 2013

Synchronized Movement and the Self-Other Boundary

I'm traveling around Britain. (Oxford, Bristol, Birmingham, Edinburgh, and St Andrews so far, Sheffield and Bristol again tomorrow and the day after.) I have some post ideas, but I'm too worn out to trust my judgment that I'll do them right, so I'm going to exert the long-time blogger's privilege of reposting something from ancient days -- 2007! Jonathan Haidt and the rubber hand illusion aren't as cutting-edge in 2013 as they were in 2007, but still....


I've been reading The Happiness Hypothesis, by Jonathan Haidt -- one of those delightful books pitched to the non-specialist, yet accurate and meaty enough to be of interest to the specialist -- and I was struck by Haidt's description of historian William McNeill's work on synchronized movement among soliders and dancers:

Words are inadequate to describe the emotion aroused by the prolonged movement in unison that [military] drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual (McNeill 1997, p. 2).
Who'd have thought endless marching on the parade-grounds could be so fulfilling?

I am reminded of work by V.S. Ramachandran on the ease with which experimenters can distort the perceived boundaries of a subject's body. For example:
Another striking instance of a 'displaced' body part can be demonstrated by using a dummy rubber hand. The dummy hand is placed in front of a vertical partition on a table. The subject places his hand behind the partition so he cannot see it. The experimenter now uses his left hand to stroke the dummy hand while at the same time using his right hand to stroke the subject's real hand (hidden from view) in perfect synchrony. The subject soon begins to experience the sensations as arising from the dummy hand (Blotvinick and Cohen 1998) (Ramachandran and Hirstein 1998, p. 1623).
The subject sits in a chair blindfolded, with an accomplice sitting in front of him, facing the same direction. The experimenter then stands near the subject, and with his left hand takes hold of the subject's left index finger and uses it to repeatedly and randomly to [sic] tap and stroke the nose of the accomplice while at the same time, using his right hand, he taps and strokes the subject's nose in precisely the same manner, and in perfect synchrony. After a few seconds of this procedure, the subject develops the uncanny illusion that his nose has either been dislocated or has been stretched out several feet forwards, demonstrating the striking plasticity or malleability of our body image (p. 1622).
So here's my thought: Maybe synchronized movement distorts body boundaries in a similar way: One feels the ground strike one's feet, repeatedly and in perfect synchrony with seeing other people's feet striking the ground. One does not see one's own feet. If Ramachandran's model applies, repeatedly receiving such feedback might bring one to (at least start to) see those other people's feet as one's own -- explaining, in turn, the phenomenology McNeill reports. Perhaps then it is no accident that armies and sports teams and dancing lovers practice moving in synchrony, causing a blurring of the experienced boundary between self and other?


Unknown said...

Super interesting post, Eric! This sounds quite plausible to me. I recently learned about Japanese precision walking/group action competitions (http://www.youtube.com/watch?v=jINuX_Hort8). It would be neat to poll precision walkers about their phenomenology.

Eric Schwitzgebel said...

Wild! Thanks for the link and suggestion, Unknown!