Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!decwrl!ucbvax!GATEWAY.MITRE.ORG!barns
From: barns@GATEWAY.MITRE.ORG (Bill Barns)
Newsgroups: comp.protocols.tcp-ip
Subject: human factors aspects of echo delay
Message-ID: <8904261932.AA00175@gateway.mitre.org>
Date: 26 Apr 89 19:32:38 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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Someone associated with NASA wrote a paper a few years ago in which he
claimed that the key parameter affecting annoyance level associated
with full-duplex typein echo delay was the variance and not the
mean/median.  (I think he was at JPL and I think his name was
Callender, but I don't remember the title or where it appeared.  Echo
delay was not the main subject of the paper but it came up in passing.)
I believe this was a qualitative/impressionistic evaluation, not a
controlled experiment.

His hypothesis would seem plausible given that there is already some
mental compensation for neurological timing skews.  I don't remember
specific numbers but have this impression of having heard that the
feedback loop time to the eye is on the order of a few milliseconds,
whereas to the toes it is somewhere in the 50+ milliseconds area.  This
is a distinguishable difference in the brain - if it weren't, auditory
direction discrimination wouldn't work.  It sounds plausible to me that
it would be easier to adapt to a high mean skew than to a high variance
of skew in echoing.  It might be amusing to speculate on whether the
echo-variance annoyance factor is due to the presence of a variance
estimator in a human user's brain processing, or to its absence.  Both
answers seem to have implicit epistemological ramifications in other
areas: the former in social sciences, the latter in physical sciences
(in which category I place protocol engineering).

Bill Barns / barns@gateway.mitre.org