COGNITIVE LOAD IN LEARNING TO USE A MULTI-FUNCTION HAND
Despite the promising functions of a multi-function hand, it is challenging to learn to use a hand that has up to 36 grip patterns. If it requires too much cognitive load to learn to operate a prosthetic hand, the user may eventually stop using it. Measurement of cognitive load while learning to use a bionic hand will help the therapist to adjust the training pace and help the user to achieve success.
An innovative, non-obtrusive method for measuring cognitive load is by tracking eye gaze. Gaze measures provide pupil diameters that indicate subjective task difficulty and mental effort. Three subjects wore a pair of Tobii eye-tracking glasses during control training and performed eight activities. Eye-tracking data were imported in Tobii Pro Lab software for extracting pupil diameter during the activities. Pupil diameter (normal range: 2-4mm during normal light) was used to indicate the amount of cognitive load.
Pupil diameters were below 4mm in 9 out of 23 training activities. Pupil diameters were above 4mm in all three subjects when they used precision pinch to perform the activities “stack 4 1-inch wooden blocks” and “pick up small objects”. Subject 3 had pupil diameters over 4mm in all training activities. Pupil diameters were largest when the subjects were adjusting the grip and when they had difficulties in initiating the grip.
It seems appropriate to introduce no more than four grips during the first control training session. Further study is required to determine if pupil diameters will decrease over time when adequate prosthetic training is given.