Differentiation of motor and cognitive load components in Fitts tapping tasks  

Manenica I., Ĺ uto A.
First author's affiliation: University of Zadar, Zadar, Croatia

The aim of this study was to try to differentiate relative contributions of motor and cognitive load components in Fitts tapping tasks (FTT) by keeping the motor component constant throughout the tasks in one situation, and comparing it with parameters in the standard situation. Twelve subjects performed the series of FTT in the standard way and in the situation with constant motor load, identical to the individual speed in the most difficult standard task. The working time for every task was five minutes. In both situations, target hits, intertap times and subjects' cardiac R-R intervals were continuously recorded. At the completion of each task subjects estimated its difficulty on Borg's scale (Borg, 1973). Performance indices (number of target hits and intertap time) changed as expected in relation to the task difficulty and the differences between the two experimental situations. Parameters and spectral analyses of R-R intervals in the middle frequency range (0.7- 0.14 Hz) showed differences in and between the two experimental situations, indicating a decrease in motor and an increase in mental component, as well as a higher overall task load in the standard situation due to a greater motor involvement. The task difficulty assessment on Borg's scale showed almost linear increase with the task difficulty, as well as a difference between the two experimental situations, indicating significantly lower task load in the situation with constant motor load. On the basis of regression lines between the task difficulty (bits) and the scale assessments in the two situations (y = 0.7+2.228x and y = -1.55+2.37x), the assessments in both situations were transformed into the difficulty equivalents in bits. The difference between the lines was equivalent to 0.71 bits, which was attributed to the differences in the motor involvement. These results showed, generally speaking, cognitive component in FTT as more prominent in task load than motor component.