Donald A. Riley & H.L. Roitblat
University of California, Berkeley
It is common observation that when we notice, think about, or observe some stimulus, it
may be difficult to notice, think about or observe other stimuli. In other words,
perception and other cognitive processes are often selective. One explanation for these
observations is that in order to notice some stimulus, we must attend to it and we can
only attend a limited number of stimuli at a time. Often, other explanations are
available. For example, it may be difficult to notice two things because they are
spatially separated, and we can only look in one direction at a time. Such peripheral
explanations are usually suggested as alternatives to an attentional explanation.
Attention can, then, be viewed as a central adaptation to information overload. There is
more information present in the stimulus array than is possible to process so it is
necessary to selectively attend to some stimuli at the expense of others.
Selective attention has also been proposed as an explanation for the performance of
animals in discrimination problems (e.g., Sutherland and Mackintosh, 1971; Riley and
Leith, 1976). Every time a selective interpretation has been proposed by some
investigator, however, other experimenters have been quick to demonstrate other more
peripheral and perhaps simpler mechanisms to account for the apparent attentional effects.
After almost 50 years it is still a matter of controversy whether an attentional
hypothesis is at all necessary to explain animal discrimination performance (Mackintosh,
This lack of resolution may be true, in part, because experimenters attempting to
investigate attention in animals have usually failed to structure their experiments to
provide any overload of the animal's ability to take in all the available information
within the allowed time. It is our view that when this condition is met, that is, when the
animal's information processing ability or capacity is taxed, the likelihood of
demonstrating selective attention will increase. The modern study of attention in humans,
beginning with Broadbent's book Perception and Communication (1958) has been
sensitive to this position. Broadbent (1961) also suggested that such a strategy would be
useful in studying animal attention.