Cognition: Memory, Attention, and Learning - Foundations for Designing User-Centered Systems - page 137

Objects in the various perceptual input buffers, such as vision and hearing, need
to be brought into memory in central cognition by a transfer process. Moving
objects into central cognition does not happen automatically, but has to done
intentionally. The amount of time the new memories are processed and how they
are processed will determine how strong the resulting memories are.
5.3.3 Divided Attention
Users who are attempting to do two tasks at the same time will have to move more
information around. They will start doing one task, and during processing on that
task they will have to notice when it is time to swap tasks and work on the second
task. In other words, they will need to divide their focus of attention between the
tasks they are performing.
How the two tasks interact will depend on several things. Users will perform
better if they can spend larger blocks of time on each task. Users that are more
practiced with each task will be able to switch more smoothly and will be able to
activate the necessary memories to assist in doing the new task faster. Practicing
doing the tasks together will also lead to better overall performance. In this case,
the user might be learning how to interleave subtasks.
Attention is influenced by both the frequency of access and type of use of items,
so dual tasks that use different perceptual buffers will interfere less with each
other. People can learn to drive and talk at the same time in normal weather
conditions, because driving does not use a lot of audio cues. That leads to the two
tasks not using the same perceptual buffers very much. At least one theory in this
area, EPIC, proposes that the only bottlenecks in performance are perception and
action (Kieras et al. 1997 ; Meyer and Kieras 1997 ).
Pairs of dual tasks, such as reading email and web browsing, based on a computer
interface will almost certainly interfere with each other to some extent. The user will
be using the same resources, including perception, aspects of cognition, and output,
typically vision, memory, and motor output, for each task. The perceptual buffer will
have to be refocused or directed to a different part of the screen. These factors will
make it harder to do each of the tasks when the other is present.
5.3.4 Slips of Action
Attention and skilled behavior have a critical role in the occurrence of slips of
action, where people have the right intention but perform the wrong action
(Norman 1981 ; Reason 1990 ). People essentially work in one of two modes:
1. Using open loop control: behavior is based on anticipation and feedforward
rather than feedback, so there is little or no need for them to monitor the result of
their actions. Other activities can be performed at the same time—automatized
driving and game play and typing are examples.