Attention Not everything that stimulates our sensory receptors is transformed into a mental representation. Rather, we selectively attend to some objects and events and ignore others. If we could not select, we would be automatons reduced to responding to whatever stimulus happened to be the strongest at any moment. Our behavior would be influenced solely by whatever thought, memory, or impulse was passing through our minds, and we would have no goal-directed control over our actions. Attention, then, is an important cognitive key to planned, adaptive behavior.
Failures of attention play a major role in several severe mental disorders. Children with attention deficit/hyperactivity disorder are extremely distractible, presumably because they cannot ignore many external stimuli. Patients with obsessive-compulsive disorder are unable to inhibit unwanted thoughts and impulses. People with schizophrenia describe a loss of mental control over both internal and external events. Similarly, individuals with depression and manic-depressive illness often report difficulties in focusing attention and in suppressing unwanted thoughts.
Psychologists have developed many ways to assess normal and abnormal attention. For example, in the "dichotic listening" task, subjects wearing earphones are asked to repeat a message sent to one ear while ignoring a different message simultaneously sent to the other ear. This task is relatively difficult when presented in similar (e.g., both male or both female) voices, but relatively easy when the two messages are presented in different (e.g., female and male) voices. In the latter case, we are greatly helped by the difference in voice quality.
In another attentional task, subjects are asked to name the ink colors in which words are printed usually done easily. But if the words are color names, such as red, printed in ink of a different color, such as blue, considerable interference and disruption can occur as people try to attend only to the ink color and suppress naming the color word.
Researchers have also examined the demands on attention when subjects search for certain "targets" in a visual display. They have found several types of situations in which focused attention is required: when separate objects that share potentially interchangeable features must be identified and located, when the target object is defined only by its lack of a feature found in all the irrelevant objects, or when feature differences are small and difficult to discriminate. Targets are easy to find if they have unique features, such as color, motion, or size. Searching for a target line among others that are slightly longer or brighter requires focusing attention on each item in turn, but a circle can easily be found in a display of lines.
Laboratory studies are examining, as well, people's ability to divide attention. In one study of distraction by internal thoughts, subjects were asked to perform mental arithmetic while watching for a particular letter to appear in a rapid sequence of other letters. As the arithmetic problems became more difficult and required more attention, the pupils of subjects' eyes enlarged (an indication of attention), and they were more likely to miss target letters.
Interestingly, people with some mental disorders, such as schizophrenia, tend to perform especially poorly on attentional tasks. Future research of this type may develop laboratory tasks that will diagnose attentional deficits with the same rigor and accuracy now used in measuring blood pressure. However, that task is likely to be complicated by the finding in both normal subjects and patients that performance on one attentional task is not necessarily correlated with performance on another. Attentional resources seem to be specific to particular sensory modalities. The more two tasks depend on the same modality, the more they are likely to compete.
Thus, we have the paradoxical finding that it is much easier to sightread piano music while repeating back oral sentences (using two different modalities vision and hearing) than it is to listen simultaneously to two different sentences (using the same modality hearing). Attentional problems may also arise when attention is divided between two tasks that both use the same modality. For example, skilled typists have difficulty taking dictation over earphones while simultaneously reading a printed passage aloud, but find it easy to repeat an oral message while performing the motor task of typing from a printed text. Future research should clarify further the attentional mechanisms through which we select and control what we see and hear, learn and remember, think and do. |
