Monday, December 03, 2007

Synchronized Movement and the Self-Other Boundary

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?


Anibal said...

This remind me an odd neurological syndrome called "enviroment dependency syndrome" that occurs when some damage or lesion affects the frontal lobe function and impairs its normal functioning (the frontal lobes are involve in impulse control, reasoning, decision, attention shift and executive functions, see L'Hermitte F. 1986)

This condition is chracterize by some blurring of the boundaries between the body of the subject and his surroundings, by which he is compell to imitate whatever movement he observes, or acting in response to evry occuring stimuli, lefting him no longer autonomous.

The limits of self- other are nowadays not very well delineated or draw, if we take into account the results emerging from a disparate of fields suggesting that perception and action are link, the evidence that some neurological disorders point to share representations of self and other information, the discovery of "mirror neurons" that fire when someone sees another performing an action but also when the subject performs the same action, and the empathy studies in ethics and morality in which the empathizer is succumbed to the emotion he witness in other(s) converting their emotion(s) in his own emotion and so on.

Eric Schwitzgebel said...

Yes, that's neat stuff, Anibal! I agree that a wide body of research suggests the self-other boundary is not as hard and fast as it might seem. (On the contracting rather than expanding side, consider "alien limb syndrome".) Thanks!

Terry A. Larm said...
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Terry A. Larm said...

Eric, I'm not sure that marching gives the same effect as the extended nose, etc. I was in the Marine Corps and did march endlessly on the tarmac. After several months there is a kind of elation that happens as you feel like the group has achieved something special, but because of proprioception there is never a sense that the others are actually part of you. I think the nose thingy only works when the subject's hand is manipulated by the accomplice, not when the subject moves it herself.

When the squad marches and (as a unit) turns left, for instance, the individual marcher experiences the world turning and the group changes form. These perceptual modifications are coordinated with the proprioceptive perceptions of personal movement and any feeling of unity that might have been developing is broken. That's why in the rubber hand experiment the subject cannot be allowed to see her own hand.

However, the sound of one giant crash of boots when I put my foot down does add to the feeling of oneness with the group, but I don't think I ever felt an extending of myself because of the crash. It seemed to be more of an emotional oneness rather than a oneness of self (if that makes any sense).

But I have to admit that it was twenty years ago that this happened to me. I do, however, have a distinct sense of accomplishment and pride as we changed from seventy people who didn't know our right foot from our left to a tight, well ordered unit. I would suspect that the feeling is more akin to that of an orchestra or quartet.

Eric Schwitzgebel said...

Thanks for those reflections, Terry! I don't necessarily disagree. (And I don't have marching experience myself.) This post is more in the speculative, what-if vein.

Your suggestion that proprioception -- or maybe more accurately the feeling of muscular control? -- interferes with the effect is interesting. I wonder what would happen to the pinnochio nose effect if the experimenter could set it up so the subject controlled her own finger. That would be tricky to do right -- but maybe if the movements were artificially constrained in some way so that the experimenter could co-ordinate his own movements....