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From: bnevin@CCH.BBN.COM (Bruce E. Nevin)
Newsgroups: comp.ai.digest
Subject: Re: I got rhythm
Message-ID: <19880918192048.4.NICK@HOWARD-JOHNSONS.LCS.MIT.EDU>
Date: 18 Sep 88 19:20:00 GMT
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Date: Thu, 15 Sep 88 09:01 EDT
From: Bruce E. Nevin 
Subject: Re: I got rhythm
To: pgoetz%loyvax.bitnet@mitvma.mit.edu, ailist@ai.ai.mit.edu
cc: bn@cch.bbn.com

Subject: Re:  I got rhythm 
In AIList Digest for Thursday, 15 Sep 1988 (Volume 8 : Issue 83), 
we read the following from Phil Goetz (PGOETZ%LOYVAX.BITNET@MITVMA.MIT.EDU):

PG> Here's a question for anybody:  Why do we have rhythm?
  |
  | Picture yourself tapping your foot to the tune of the latest Top 40
  | trash hit. . . . Different actions require different processing
  | overhead.  So why, no matter what we do, do we perceive time as a
  | constant?  Why do we, in fact, have rhythm?  Do we have an internal
  | clock, or a "main loop" which takes a constant time to run?  Or do we
  | have an inadequate view of consciousness when we see it as a program?

The music has rhythm.  The foot tapper has synchrony.

There are lots of physiological processes that are rhythmical in nature,
and with which one can synchronize other behavior.  Some are ongoing,
notably heartbeat, breathing, and brain waves.  Others are easier to
start and stop, like walking or running.

However it's done, it seems straightforward for organisms to set up an
ad hoc oscillation, as in shivering, rubbing hands/paws together,
pacing.  For such activities it seems plausible that the governing
mechanisms are encapsulated and require little attention.  Minsky's
_Society of Mind_ is a good place to look.  (Open question how ad hoc
they are, perhaps they are in synchrony with preexisting rhythms.)

The musicians (and not just the toe tappers and other dancers) are also
synchronizing their actions with respect to existing rhythms, even if
only to a beat counted out by the leader of the band at the outset
(a-one, and a-two . . . ).  Where does the initiating musician get the
rhythm?  Heartbeat?  Imagining/ remembering oneself walking?  (That is
the meaning of `andante'.)  Imagining/remembering people dancing?
Certainly, once they have started, members of the band must synchronize
their playing with one another (ensemble).

What happens when the foot tapper is preoccupied with other thoughts?
The tapping doesn't slow down, it can't because synchrony is essential
to it.  Instead, it becomes sporadic.  The process itself gets dropped
and picked up again.  Just so, new musicians have to practice keeping up
a steady rhythm despite being distracted by other things (coordinating
fingers on the instrument, remembering the words in a song).  Their
novice performance is typically marked by interrupting and resuming the
given rhythm.  If a practicing pianist slows down in a passage where the
notes are small and close together, it is mostly to coordinate the
fingers physically, not to free up processing time.  (Preferred way is
to slow the whole piece down and play at a constant tempo.)

It seems to require a certain amount of attention to maintain a rhythmic
behavior, presumably above the threshold required to maintain synchrony.

But that's not much, as anyone can attest who has discovered her or his
body swaying or falling in step or tapping unawares during a
conversation.

Rhythm (cyclicity) is an environmental given.  Resonance (entrainment)
is also a given in physics, ecology, psychology.  Music and dance play
with these givens.

Seems to me that cyclicity and synchrony has survival value in that it
helps make organisms predictable to one another.  Creatures that become
prey are typically those unable to maintain synchrony with their social
group because of sickness, etc.  Stricking examples of synchrony include
flocks of birds, schools of fish.  We have recently heard of LIFE
emulations of flock behavior involving little processing overhead.

Perhaps the problem is not how do individuals synchronize in a flock,
but rather how does individuation happen out of the flock, and to what
extent.  It seems plausible that the experience of being an independent
ego that we humans cherish is an illusion.  To maintain such an
illusion, we ignore counterevidence.  A pretty good definition of
unconscious behavior.  (Say, did you know your foot was tapping?)

Bruce Nevin
bn@cch.bbn.com