Cognition: Memory, Attention, and Learning - Foundations for Designing User-Centered Systems - page 126

(a) (b)

1 2 3

1 2 3

4 5

4 5

6 7 8

6 7 8

Type in the tile to move [1-8]: ____

Click on the tile to move
into the empty space.

Type in direction to move [N/S/E/W]: ____

Fig. 5.2 Two types of interfaces for the 8 puzzle that lead to different types of learning.

a Interface leading to more explicit representation. b Interface leading to more implicit

representation

Some procedural information, such as how to use the Emacs text editor, a
keystroke driven editor, starts out fairly explicit in that the user can describe what
they are doing and why. Over time procedural information, or skills learned
through trial and error without explicit, declarative reflection, can become implicit.
In this case, the user can recognize objects, can have a way of performing a task
but without being able to note why or how, and in some cases cannot even be able
to recognize that they can do the task well. If the information remains in explicit
memory users can perform tasks more robustly and, because they can describe how
to do the tasks, they can help others more readily.
Users can be encouraged to store information in explicit memory by helping
them develop a mental model of a task, and by providing them with time to reflect
on their learning. Information gets put into implicit memory when the user works
without a domain theory and learns through trial and error.
Work with the 8-puzzle (see Fig. 5.2 ) has illustrated this effect in interfaces. In
this puzzle there are eight tiles and nine spaces. The task is to arrange the tiles in
numerical order (left to right, top to bottom). The interface in Fig. 5.2 a requires
users to note the tiles that had to be moved and where to move them to, as a way of
encouraging users to plan and think ahead. It also provided them with an explicit
representation of steps for their reflection. Users that saw the interface that
required only clicking on the tile to move it into the adjacent blank space
(Fig. 5.2 b) needed less explicit input and appeared to encourage behavior that led
to less information being stored in memory.
In the first interface subjects reflected on their moves and developed an explicit
representation of the problem. They took fewer moves to perform the task than those
who used the second, direct manipulation, interface (although they took more time).