Effect of task difficulty and angle in a positioning task involving symmetrical and asymmetrical motions

Abstract

Task difficulty where simultaneous hand motions are involved may be defined for a given angle(s) of hand motion, as the magnitude of hand motion and the amount of control needed for completing the hand motions. The task difficulty has traditionally been measured using the following relationship: TD = log₂ 2D/C bits where D is the distance moved and C is the target diameter. Task difficulty and its effect on element position involving symmetrical and asymmetrical simultaneous motion does not seem to have been investigated in the past. In this paper results of experimental investigations are reported. The experiments included nine levels of task difficulty and three angles of hand motion for each symmetrical and asymmetrical simultaneous motion, Models for predicting performance times for ‘position’ involving symmetrical and asymmetrical simultaneous motions have been developed. A comparison of predicted time values using these models has been made with the values developed using some of the available predetermined motion time systems.