[From Bruce Abbott (960710.2045 EST)]

Bill Powers (960710.1430 MDT)] --

    Bruce Abbott (960710.1035 EST)

    To achieve synchrony of two (or more) oscillators, all that is
    required is negative feedback.

Actually, no feedback at all is needed. Synchrony of free-running
oscilllators can be achieved simply by perturbing them at intervals
close to the free-running frequency, like pushing on a pendulum at
nearly the same point in each cycle.

And how does "perturbing them at intervals" bring them into synchrony? I
don't follow. I can see how that would alter their periods (temporarily),
but why would they synchronize as a result? I'm not assuming that the two
oscillators have the same periods, although they would be within a few
percent of each other. When you were a kid and trying to get the swing to
go as high as possible, did you find that if the kid in the next swing was
doing the same thing that the two of you were thereby brought into
synchrony? I don't recall that being the case in my experience, not unless
I were actually trying to bring that about AND the two swings had the same
length of chain.

The reason I don't think that menstrual cycles are under control is
precisely that they can be synchronized by such minor influences as
pheremones. If they were actually under control (with respect to
frequency or phase) it would be difficult to change them. The fact that
a few molecules of a chemical can alter the cycle doesn't show that the
chemicals are superpowerful; it just shows that what they're affecting
isn't hard to change.

I don't think that menstrual cycles are under control either, but for a
different reason: even if synchronization were highly adaptive, it can be
accomplished by simple means that do not require the relatively elaborate
machinery of a control system. As to the effect of a few molecules of
pheromone, what they're affecting could be exceedingly difficult to change
by other means, or easy. The fact that pheromones can have this effect
really says nothing at all about the ease with which other inputs may affect
the cycle.

By the way, I seem to have left all the middle "o"s out of "pheromone" in my
last post. As a result I have several extra "o"s cluttering up my desk; if
anyone would like them, just ask and I'll send them along.