[Sensitivity and diagnostic value of mental load in a secondary task on tapping rate]

When executed concurrently with a primary task, finger tapping performance is commonly interpreted as an indication of the primary task mental workload. Higher load during tapping induces an increase in mean or variability of intertap intervals. Finger tapping sensitivity was tested with series of 13 taps at a tapping rate of one tap every two seconds. Concurrent primary task required subjects to search for a target item, presented after each tap, in a three digit memory set memorized before each series. Processing load was varied by including letter targets amongst positive and negative digit targets. Letter target recognition should require less processing than digit recognition. Results show mean intertap intervals for letter targets to be shorter than for negative digit targets. Furthermore, recognition of negative digit targets induces a longer mean intertap interval than positive targets. These data suggest that continuous finger tapping is a sensitive index of the mental workload originating from working memory processing requirements. However, analysis of practice data show that development of strategies at performing the dual task may mask the sensitivity of the finger tapping task.