Continuous attention: rationale and discriminant validation of a test designed for use in psychopharmacology

The continuous attention task (CAT) is a test designed to assess changes in attention due to a variety of factors, for example, drugs. Subjects view a series of 3x3 patterns of squares on a monitor screen, each displayed for 100 msec at intervals of 1.5–2.5 sec, and respond whenever two successive patterns are identical. For such a measure to be validr factors other than attention should be investigated, and shown not to be a factor in performance. Nineteen subjects took part in a study in which information-processing rate and recall of CAT figures was measured. The results showed that a viewing time of 50–60 msec was sufficient for 50% correct recognition of CAT figures, and that recognition with a masked presentation of 100 msec did not differ significantly from an unmaske presentation of 100 msec. Mean recall of CAT figures 2 sec after a 100-msec exposure was 98.2%. These results suggest that performance on the CAT is not limited by either information-processing speed or memory capacity, but is a valid measure of the ability to sustain attention.