We investigate the form and time course of motion adaptation, comparing the psychophysical performance of human subjects with existing electrophysiological data on insect vision. In the H1 neuron of the fly, the response to a maintained motion stimulus is known to decrease over time while sensitivity to variations in speed around the maintained level increases. This behaviour can be modelled by modifying a correlation-based motion detector to include adaptable temporal filters (Fig. 1). We find that the form and time course of sensitivity changes in human motion perception are comparable to fly vision. We propose that, in both cases, adaptation serves to improve the transmission of novel motion information along the visual pathways at the expense of maintaining an accurate representation of the unchanging components of the stimulus.