relevant in the context of our present activities and goals. That is true as far as
it goes, but attention is sometimes ‘‘captured’’ involuntarily by certain stimuli.
For example, Muller and Rabbitt (1989) instructed their subjects to allocate vi-
sualattentiononthebasisofanarrowandtoignorebrieflybrightenedsquares
presented in the periphery of vision. In spite of these instructions, subjects’ at-
tention was drawn to the brightened squares.
There is an important distinction between focused and divided attention (see
figure 15.1). Focused attention is studied by presenting people with two or
more stimulus inputs at the same time, and instructing them to process and
respond to only one. Work on focused attention can tell us how effectively
people can select certain inputs rather than others, and it enables us to investi-
gate the nature of the selection process and the fate of unattended stimuli.
Divided attention is also studied by presenting at least two stimulus inputs at
the same time, but with instructions that all stimulus inputs must be attended
to and responded to. Studies of divided attention provide useful information
about an individual’s processing limitations, and may tell us something about
attentional mechanisms and their capacity.
There are two important limitations in most research on attention. First, al-
though we can attend to either the external environment or the internal envi-
ronment (i.e. our own thoughts and information in long-term memory), most of
the work on attention has been concerned only with attention to the external
environment. Why should this be so? Experimenters can identify and control
the stimuli presented in the external environment in a way that is simply not
possible with internal determinants of attention.
Second, as Tipper, Lortie, and Baylis (1992) pointed out, most studies of
attention are very artificial. In the real world, we generally attend to three-
Figure 15.1
The ways in which different topics in attention are related to each other.
364 Michael W. Eysenck and Mark T. Keane