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From: norman%ics@UCSD.EDU (Donald A Norman-UCSD Cog Sci Dept)
Newsgroups: comp.ai.digest
Subject: Lightbulbs and Related Thoughts
Message-ID: <8811160002.AA16066@sdics.ICS>
Date: 16 Nov 88 00:02:18 GMT
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Iconic memory is the brief, reasonably veridical image of a sensory
event.  In the visual system, it has a time constant of somewhere
around 100 msec.  Visual iconic memory is what makes TV and motion
pictures possible: 30 to 60 images a second fuse into a coherent,
apparently continuous percept.  I demonstrate this in class by waving
a flashlight in a circle in a dark auditorium: I have to rotate about
3 to 5 times/second for the class to see a continuous image of a
circle (the tail almost dying away).

The illustration of seeing complementary colors after staring at, say,
an image of a flag, is called a visual after effect, and is caused by
entirely different mechanisms.

don norman

Donald A. Norman	[ danorman@ucsd.edu   BITNET: danorman@ucsd ]
Department of Cognitive Science C-015
University of California, San Diego
La Jolla, California 92093 USA

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