[FRIAM] bilateria

[Stephen Guerin]

> Eric writes
>  When I was a kid, there was some article (maybe Sci. Am.?) that I found
wonderful.

Bilateral Symmetry may apply to in magazines too :-) Here's a 1973 article
in "American Scientist" instead of "Scientific American" :-)

https://www.americanscientist.org/article/how-the-owl-tracks-its-prey
from the article:
Asymmetrical placement of the ears (one higher than the other) allows the
owl to determine both the azimuth (horizontal direction) and elevation
(vertical direction) of sounds.


On Mon, Jul 14, 2025 at 2:33 PM Santafe <desmith at santafe.edu> wrote:

> > On Jul 15, 2025, at 2:41, glen <gepropella at gmail.com> wrote:
> >
> > Now, I'm sensitive to the argument that all this falls under parallax,
> even radially symmetric body types and the 9 octopus ganglia. And bi-
> vision, hearing, etc. is a simple form of parallax: triangulation.
>
> When I was a kid, there was some article (maybe Sci. Am.?) that I found
> wonderful.
>
> It had to do with owl ear asymmetries, which are produced by tufts of
> stiff feathers at unequal positions in front of whatever feather-hood (or
> something) channels sound to the ear canals.
>
> Upshot of the articles was that owls need resolution in the vertical as
> well as the horizontal, from phase, intensity, and packet-arrival-time
> differences (including what acousticians term the “head-shaped transfer
> function”, as I learned some decades later working among the acousticians
> for a few years).
>
> Article claimed (I have no way to check without a dive to see what has
> been done since) that owls and people have about the same acuity in lateral
> position of a sound’s origin, if the sound has enough shape (so, not a
> clarinet) to cue from.  But people have terrible vertical acuity.  For
> owls, the vertical acuity is ballpark-comparable to the lateral.
>
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