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From: norman@sdics.ucsd.EDU (Donald A. Norman)
Newsgroups: comp.cog-eng
Subject: Re: Request for human interface design anecdotes
Message-ID: <408@sdics.ucsd.EDU>
Date: Thu, 12-Nov-87 06:18:29 EST
Article-I.D.: sdics.408
Posted: Thu Nov 12 06:18:29 1987
Date-Received: Sat, 14-Nov-87 17:51:27 EST
Reply-To: norman@sdics.UUCP (Donald A. Norman)
Organization: UC San Diego Institute for Cognitive Science
Lines: 75
Keywords: human factors, interfaces, design

A common form of error results from incompatible standards.  When one
system uses one technique and another system a different technique for
the same result, or the same technique for a different result, capture
error is likely, where the more frequently invoked procedure is
performed instead of the intended less-frequently performed one.

Examples:
======================================================================
VI text editor               UCSD Pascal text editor

ESC => accept typed material	ESC => abort -- destroy typed material
                                 (with no recovery possible)

(the vi editor and UCSD pascal editors were frequently used by the same
people here at UCSD.  The incompatibility is perhaps understandable
because vi didn't exist when UCSD pascal was developed, but the lack
of an undo on the UCSD Pascal system is not excusable).  had there
been an undo, the noise level around here would have been considerably
less. 
======================================================================
SUN window system               Macintosh multifinder
                                Symbolics window system

To direct text to any window on the screen (i.e., to make that window
active)

place mouse cursor over window     place mouse cursor on window and
                                    CLICK

To move text into the internal buffer (clipboard) for a copy --paste
sequence

highlight desired region           highlight desired region and type
                                    command-c   (or select "copy")

The lack of clicks on the sun, either to activate the window or to do
their equivalent of "copy" constrasts with the clicks required with
other systems leads to much eror and confusion when the two systems
are used by the same people.  The errors are frequent (I use a
macintosh and sun next to one another, and this very minute I am using
my sun via my macintosh).  Because both systems are pretty robust,
with powerful undos, the problems are usually not serious, unless you
accidentlaly move the mouse cursor to the emacs window on the sun and
type, in which case wild things can happen.   There really ought to be
a more visible indication of which window is active and, in the case
of the copy command, of the fact that matrerial is in the clipboard or
copy buffer (the old Xerox Bravo editor used to display the contents
of the copy buffer at all times -- that really helped.)

======================================================================
Britain                             United states

light switches: up = off            up = on
======================================================================
Britain, Japan, ..                 United states

auto drives on left                auto drives on right

car in round-about (circle)         car in roundabout (circle)
has right of way                    must yield to  entering autos

(These are included to indicate that problems are not restricted to
computer design.  Note that when one takes the ferry between the
continent and britain, the lack of compatibility makes for immediate
diffiuclties with surprisingly little warning or guidance on either
side.) 

don norman

Donald A. Norman
Institute for Cognitive Science C-015
University of California, San Diego
La Jolla, California 92093
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