Discovering the constraints of state change in a bimanual coordination task

Prof. Tin Cheung Chan
Ph.D., University of Connecticut
Department of Psychology,
The Chinese University of Hong Kong

Abstract

Movement is intrinsically related to cognition, intelligence and pathology. In fact, most of the cortex is attributed to perception and action.
Kelso (1981), in the effort of studying state change in walking, used finger movement for simulation. He showed a state change in finger movement as in walking. Participants swung their index fingers simultaneously from side to side (anti-phase motion) from slow to fast speed. If the frequency was increased beyond a critical value, such swing will collapse into swinging from both sides to the midline and vice versa (in-phase motion). This shift (called critical phase shift) can be described mathematically and can be measured in EEG. Yet, what is the psychological explanation for such a state change? Cohen (1973) explained the shift as the taking over of the more controllable homologous muscles from the non-homologous muscles. However, Mechsner, Kerzel, Knoblich, and Prinz? (2001), showed that with the right hand in pronation (palm face downwards) and the left supination (palm face upwards), anti-phase motion with non-homologous muscles actually was easier to operate. Similarly, with both hands in pronation, participants performed synchronous taping with the middle and index fingers of the left hand and with the ring and middle fingers of the right hand. It was easier to tap the middle finger of the left hand synchronously with the ring finger of the right hand than otherwise. This shows that spatial symmetry is a better explanation. Yet spatial symmetry is a description rather than an explanation. Our muscle movement must have certain intrinsic constraints to produce such bias to spatial symmetry. My talk will show you the story of the discovery of such constraints. The discovery of a better explanation is the excitement for a scientist.