ABSTRACT
Ecological and physiological evidence suggests that motion should be very important in the vision of birds, as it is in human vision. However, because of technical difficulties, and uncertainty about the suitability of current video and computer technology for presenting moving stimuli to birds, there has been relatively little research on avian perceptual and cognitive processing of motion. The present article first reviews what we know about birds' processing of moving video images. Although the bird's eye view differs from the human view, static video images are effective stimuli for birds, and pigeons can respond to apparent motion as though it was real motion. Using video images, birds have been shown to discriminate still from moving images, between moving shapes, and between categories of movement. There is some but not complete evidence of transfer between moving video images and the real objects they represent. Movement may aid the process of feature integration, and it gives rise to some but not all of the cognitive effects that it leads to in humans — for example birds do seem to track a temporarily invisible moving object correctly, but they do not respond distinctively to causal movements. Secondly, the paper reviews some questions that are now open for research, but have not yet been properly addressed, for 144example the psychophysics of video images, the relative salience of movement cues in pattern discrimination, movement after effects and the role of movement in depth perception and individual recognition. There remain some things we can never know about how birds see video stimuli, because of problems that include the impossibility of sharing the subjective experience of any other individual, or of entering into the perceptions of animals whose perceptual and cognitive processes and experience are different from our own.
