Accuracy of boundary detection by observers of filmed movement

The influence of filming speed and body-part velocity on observers' accuracy during the microanalysis of filmed movement was investigated. Four experienced observers analyzed a stimulus film containing initiation and termination boundaries in the movement of a rod oscillating at rates derived from a range of filming speed and body-part velocity combinations. Results indicated that greatest errors in boundary-frame detection occurred at the fastest filming speed and slowest body-part velocity. Furthermore, a boundary-type effect was significant, with initiations being harder to detect accurately than terminations. Attention was drawn to the complexity of microanalysis, and it was suggested that expectations of unconditional absolute accuracy on this task are unrealistic.