The coupling between point-of-gaze and ball movements in three-ball cascade juggling: the effects of expertise, pattern and tempo.

The relationship between point-of-gaze and ball movements in three-ball juggling was examined as a function of expertise, pattern and tempo. Five intermediately skilled and five expert jugglers performed the standard and reverse cascade at three tempos, while point-of-gaze and ball movements were recorded simultaneously. Scaled to the size of the ball patterns, the experts made smaller point-of-gaze movements than the intermediates, especially in the horizontal direction and in the standard cascade. In both skill groups, point-of-gaze and ball movements were often 1 : 1 frequency locked in the horizontal direction, whereas in the vertical direction 1 : 2 frequency locking also occurred. In the latter direction, the 1 : 1 ratio prevailed in the intermediates and the 1 : 2 ratio in the experts. In addition, the incidence of the 1 : 1 ratio decreased and that of the 1 : 2 ratio increased with increasing tempo. Furthermore, in the vertical direction, increasing tempo resulted in a weaker 1 : 1 locking, whereas the strength of the 1 : 2 ratio remained unaffected by tempo. In the horizontal direction, the strength of the 1 : 1 locking was higher on average in the reverse cascade than in the standard cascade. We conclude that expertise in juggling is reflected by an overall reduction in the extent to which the balls are visually tracked, and that task constraints such as tempo and juggling pattern affect the visual search patterns of both expert and intermediate jugglers.