Considerations in video playback design: Using optic flow analysis to examine motion characteristics of live and computer-generated animation sequences

The increasing use of the video playback technique in behavioural ecology reveals a growing need to ensure better control of the visual stimuli that focal animals experience. Technological advances now allow researchers to develop computer-generated animations instead of using video sequences of live-acting demonstrators. However, care must be taken to match the motion characteristics (speed and velocity) of the animation to the original video source. Here, we presented a tool based on the use of an optic flow analysis program to measure the resemblance of motion characteristics of computer-generated animations compared to videos of live-acting animals. We examined three distinct displays (tail-flick (TF), push-up body rock (PUBR), and slow arm wave (SAW)) exhibited by animations of Jacky dragons (Amphibolurus muricatus) that were compared to the original video sequences of live lizards. We found no significant differences between the motion characteristics of videos and animations across all three displays. Our results showed that our animations are similar the speed and velocity features of each display. Researchers need to ensure that similar motion characteristics in animation and video stimuli are represented, and this feature is a critical component in the future success of the video playback technique.