We examined the relationship between dexterity and movement to facilitate picking
up visual information in a skilled task, the kendama trick of “swing-in.” Two kendama
experts performed the swing-in motion while wearing liquid crystal occlusion goggles in
the control and experimental (occluded) conditions. Occlusion glasses were open in the
control condition, but open and closed at pre-set intervals in the occluded condition.
After practice, the results identified a preference for seeing of the zenith of the ball
trajectory for both experts at all levels in the occluded condition. Ball movement in the
anterior-posterior axis for both experts was larger in the occluded than in the control
condition, and was changed by the opening time of the goggles for expert A. Head
movement in the vertical axis for both experts was longer in the occluded than in the
control condition, but changed by the goggle’s intervals for expert B. Ball velocity with
the coordinate origin at the head for both experts was nearly constant when the ball
trajectory was near the zenith in both conditions and when the goggles were open in
the occluded condition. However, the orientation of the head was longer in the occluded
than in the control condition.
These findings suggest that both experts detected optical information for catching
the ball when the ball trajectory was near its zenith in intermittent viewing conditions,
and that it is easier pick up this information in the occluded condition due the longer
duration of the nearly constant relative velocity of the ball. Both experts adjusted their
actions to easily detect the necessary optical information under visual constraints, al-
though expert A adjusted the movement of the ball and expert B adjusted his head
movement to the goggle’s opening intervals.
