A multi-level approach to investigate the control of an input device: application to a realistic pointing task

Abstract

This study investigates the subjects' performance during realistic conditions of control of a joystick. An adapted reciprocal aiming task consisting in driving a virtual vehicle along a slalom course as fast as possible was performed while accuracy constraints were manipulated. Realistic dynamical Interface Screen Relationship between the joystick displacements and the displacements of the vehicle was simulated. Vehicle displacements and motor activity (muscle activity and joint kinematics) were recorded. The results highlighted the applicability of the Fitts' law to more realistic conditions where the use of an input device is performed in an intensive control situation. Besides, biomechanical results suggested that neuromuscular responses were different regarding the direction of movement, whereas the performance at a behavioural level were not affected. Thus, this study demonstrates the interest in considering two different aspects of the user's performance (behavioural and biomechanical ones) to make a better agreement between the device design and users' needs.

Abstract

Practitioner Summary: This study considered two different aspects of the subject's performance in a realistic situation of speed–accuracy trade-off: the behavioural and motor activity. The necessity for the design of the future ergonomics pointing devices to meet the expectations of the neuromuscular system in order to facilitate their uses is highlighted.

Keywords::

• input device
• user performance
• motor control
• biomechanics
• multi-level analysis

Notes

^1. In classical Fitts' law studies, the error rate is generally kept under about 5%. However, in the present study, participants performed a more complex task because (1) a non-linear ISR relating control input to device output was used (see experimental set-up) and (2) the nature of the aiming task involved control of displacements of the vehicle along two orthogonal axes simultaneously.