Drag & Drop: Usability Information 
Author Message
 Drag & Drop: Usability Information

Recently, there has been some discussion on implementing Drag & Drop.
I thought people would be interested in this article which recently
appeared in our newsletter, Eye For Design.  (See end of the article
for information on getting a free issue.)


In testing the designs of several client's products, we've observed
several issues related to how users learn drag and drop operations.
While drag and drop can improve a user's productivity considerably, if
they can't learn how to use it, the benefits will not be realized.
Here are some of the problems we've observed.

Users May Not Expect It

User expectations are often shaped by other products that they've
worked with.  However, we've observed that drag and drop experiences
always seem to translate well to new products.

For example, just because users have dragged files in the Windows 3.1
File Manager doesn't mean that they look for drag and drop capability
in some other application.  Users don't see the File Manager as an
application.  (It appears as a piece of a bigger thing -- the
operating environment.)    Therefore, they don't seem to connect that
an application's interface might be similar to the File Manager.  In
testing other applications, we've seen that users are often not aware
of drag and drop methods, and have to learn about them in each

Since every application that implements drag and drop seems to
implement it slightly differently, it's no wonder that users have
trouble transferring knowledge from one application to another.

It's Only A Shortcut

We've observed that new users typically learn product functions from
menus or toolbars then "graduate" to faster methods such as
double-clicking and drag and drop.  If there is functionality that can
only be accomplished by drag and drop, users may never find it at all.
 We saw this in the Lotus 1-2-3 dialog box for editing SmartIcons --
users didn't realize they were supposed to drag icons from one list
box to another.

Four Things To Learn

Users must learn four concepts to use drag and drop effectively:

1) "What objects can I drag?"
2) "Where can I drop them?"
3) "What's it going to do when I let go?"
4) "If I don't like it, how do I undo it?"

No Clues

The first two questions arise when clues are missing.  Drag and drop
isn't readily visible.  Users must learn that it exists through some
external mechanism.

One development team we worked with tried a visual cue, using a small
blue square to indicate a draggable object.  Users didn't get it. The
team then tried another tack: illustrating the drag and drop
capability on a mockup of the product box.  This worked better --
users picked up on the drag and drop capability and used it
successfully.  Caveat: we don't know whether in real life users would
have looked at the box!

What's The Verb?

The "what's it going to do?" issue arises because the verb is implied
by a drag and drop operation often depends on the context.  Consider
the Windows 3.1 File manager, where dragging a file to a directory on
the same disk moves the file, but dragging a file to a different disk
copies it.  Same drag and drop, but two different verbs are implied
depending on the relationship between the source and destination.

Cursor icons can provide clues, but users must still learn what the
different icon mean.  Microsoft Publisher tries an interesting idea:
attaching words to cursor icons.  For example, the "Move" icon shows a
picture of a truck with the word "Move" on it.  Although we have not
tested drag and drop in Publisher, we do have ample evidence that an
icon and word approach improves recognition for toolbar icons.

How Do You Undrop?

Since drag and drop can have destructive consequences, users need a
way to undo drag and drop they didn't intend.  In one test, we saw
several users accidentally destroy spreadsheet charats as follows:

* User wants to move entire chart, but positions the mouse insed the
chart and drags just part of the chart

* User notices error an makes an unsuccessful attempt to drag it back
the way it was

* User tries undo, but it only undoes the last action (the attempted
correction, not the accidental drag)

* After a few more attempts to correct the chart manually, user
deletes the chart and re-creates it

Thus, adding drag and drop capability to an interface may increase the
need for verification questions and/or multiple levels of undo.


User Interface Engineering produces a bimonthly newsletter called Eye
For Design, which contains the latest tips and techniques for
developing excellent applications. You'll read about the latest
research we've done on how to build usable applications.

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(c) 1995, 1996 User Interface Engineering

 Jared M. Spool                User Interface Engineering

 (508) 975-4343                   North Andover, MA 01845
 fax: (508) 975-5353                                  USA

      If you send me your postal address, you'll get
     the next issue of our newsletter, Eye For Design.

Fri, 10 Jul 1998 03:00:00 GMT
 [ 1 post ] 

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