Tapping task as an index of mental workload in a time sharing task1

The sensitivity of tapping task to mental workload was investigated. Thirteen subjects were asked to produce 3 s intervals continuously while performing a time sharing task. The time sharing task was designed to manipulate a demand to allocate an attentional resource to one target and a demand to switch the target to which an attentional resource was mainly allocated. Results showed that produced intervals became shorter and more variable as the time sharing task became more demanding. The subjective workload assessment by the NASA Task Load Index (NASA-TLX) indicated that subjects experienced an increasing workload as the demand of the time sharing task increased. Two sub scales of the NASA-TLX, “effort” and “mental demand,” were rated higher than other sub scales. These results suggest that the tapping task is sensitive not only to the motor output load but also to the central processing load.