Abstract
Without training, people can only perform two modes of rhythmic coordination stably – 0o and 180o relative phase. For both bimanual and unimanual coordination, as frequency increases, stability decreases, and performance of 180o phase switches to 0o. With training, people learn other coordination patterns, including 90o. In the current study, we tested whether skilled performance of 90° coordination would exhibit phase switching with frequency scaling, as does 180°. Participants were trained to perform 90o bimanually, at 0.75 Hz until they reached a mean proportion of time spent at 90o +/- 20o of 0.60 across 24 trials. Then, after 5 practice trials performing 90o unimanually, participants completed two series of trials with frequency scaling performing 90o bimanually and two unimanually. In one series of each condition, participants viewed the joysticks they were moving and in the other they viewed moving dots on a display controlled by the joysticks. Results showed no difference in mean performance between joystick and display conditions. 90o coordination did not exhibit phase switching to 0o or 180o as frequency increased. In agreement with previous studies, bimanual performance was better than unimanual. We divided the data into 20o relative phase bins from 0o to 180o to reveal the time spent at each relative phase. Unimanual and bimanual conditions exhibited different distributions, with bimanual showing greater proportions of time spent in the phases close to 90o and unimanual showing more evenly distributed times across all phases. Unimanual performance also showed a significant effect of frequency within each phase bin, with better performance at 1 and 1.25 Hz, while bimanual performance showed no difference. Increasing frequency did result in lower stability for unimanual as compared to bimanual performance. The lack of phase switching likely indicates use of different information to perform 90o as compared to 0o and 180o.
Meeting abstract presented at VSS 2018