Attention-switching and grouping in counting interaurally presented clicks.

The present study tests the hypothesis that attention-switching is time-consuming and performance-limiting. Analysis of previous research on counting interaurally presented clicks shows that estimates of ‘switch-times’ can be made, based on the data of Guzy and Axelrod (1972). In the earlier click-counting studies, however, the number of clicks to be counted and the number of physical switches between the ears were confouned. Hence the number of clicks, number of physical switches and interval between clicks were independently varied. The results showed that (a) counting performance did not decrease monotonically with increasing number of switches in the click sequence; (b) no difference in counting performance could be found between the monaural and completely alternating interaural presentation; (c) when the number of switches in the sequence was small and equal groups of clicks alternated between ears, performance dramatically improved. With these kinds of sequences, subjects presumably do not count the clicks one at a time, but subitize a group of clicks.