Identifying perceptual thresholds is critical for understanding the mechanisms that underlie signalevolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jackydragon Amphibolurus muric...Identifying perceptual thresholds is critical for understanding the mechanisms that underlie signalevolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jackydragon Amphibolurus muricatus, a species that makes extensive use of rapid motor patterns in so-cial communication. First, focal lizards were tested in discrimination trials using random-dot kine-matograms displaying combinations of speed, coherence, and direction. Second, we measuredsubject lizards＇ ability to predict the appearance of a secondary reinforcer （1 of 3 differentcomputer-generated animations of invertebrates： cricket, spider, and mite） based on the directionof movement of a field of drifting dots by following a set of behavioural responses （e.g., orientingresponse, latency to respond） to our virtual stimuli. We found an effect of both speed and coher-ence, as well as an interaction between these 2 factors on the perception of moving stimuli.Overall, our results showed that Jacky dragons have acute sensitivity to high speeds. We then em-ployed an optic flow analysis to match the performance to ecologically relevant motion. Our resultssuggest that the Jacky dragon visual system may have been shaped to detect fast motion. Thispre-existing sensitivity may have constrained the evolution of conspecific displays. In contrast,Jacky dragons may have difficulty in detecting the movement of ambush predators, such as snakesand of some invertebrate prey. Our study also demonstrates the potential of the computer-animated stimuli technique for conducting nonintrusive tests to explore motion range and sensitiv-ity in a visually mediated species.展开更多
文摘Identifying perceptual thresholds is critical for understanding the mechanisms that underlie signalevolution. Using computer-animated stimuli, we examined visual speed sensitivity in the Jackydragon Amphibolurus muricatus, a species that makes extensive use of rapid motor patterns in so-cial communication. First, focal lizards were tested in discrimination trials using random-dot kine-matograms displaying combinations of speed, coherence, and direction. Second, we measuredsubject lizards＇ ability to predict the appearance of a secondary reinforcer （1 of 3 differentcomputer-generated animations of invertebrates： cricket, spider, and mite） based on the directionof movement of a field of drifting dots by following a set of behavioural responses （e.g., orientingresponse, latency to respond） to our virtual stimuli. We found an effect of both speed and coher-ence, as well as an interaction between these 2 factors on the perception of moving stimuli.Overall, our results showed that Jacky dragons have acute sensitivity to high speeds. We then em-ployed an optic flow analysis to match the performance to ecologically relevant motion. Our resultssuggest that the Jacky dragon visual system may have been shaped to detect fast motion. Thispre-existing sensitivity may have constrained the evolution of conspecific displays. In contrast,Jacky dragons may have difficulty in detecting the movement of ambush predators, such as snakesand of some invertebrate prey. Our study also demonstrates the potential of the computer-animated stimuli technique for conducting nonintrusive tests to explore motion range and sensitiv-ity in a visually mediated species.
