Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!lts!amanda@lts.UUCP
From: amanda@lts.UUCP (Amanda Walker)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: human factors aspects of echo delay
Message-ID: <01-May-89.183043@192.41.214.2>
Date: 1 May 89 22:22:57 GMT
References: <8904261932.AA00175@gateway.mitre.org>
Sender: news@lts.UUCP
Reply-To: amanda@lts.UUCP (Amanda Walker)
Organization: InterCon Systems Corporation, Sterling, VA
Lines: 22

I'm not sure where I picked up this figure (probably psychology readings
for a course or something similar), but as I remember, the basic "cycle
time" of conscious processing is about 1/20th of a second, i.e. events
occurring at 50ms intervals are greater can be perceived as separate
events, whereas events occurring at shorter intervals are perceived
as simultaneous, depending somewhat on what kinds of events are being
correlated.  For example, a video terminal running at 300 baud in
full duplex gives most people the illusion that the letters are appearing
as they type (66ms).  However, motor skills (such as tracking moving
objects) involve much more fine-grained timing (hmm... hardware buffers :-)?)
For example, animation at 60 or 120 frames/sec will look much smoother and
more "realistic" than at 30 frames/sec, even if there's no consciously
perceptible flicker...

Part of the point of this is that how fast the feedback needs to be depends
a lot on what you're feeding back.  Keystrokes can probably get by with
50-80ms.  Rubber-band lines need to be 15-30ms, and so on.

--
Amanda Walker
InterCon Systems Corporation
amanda@lts.UUCP / lts!amanda@uunet.uu.net