To CD or not to CD: Is there a 3D motion aftereffect based on changing disparities?

Recently, T. B. Czuba, B. Rokers, K. Guillet, A. C. Huk, and L. K. Cormack, (2011) and Y. Sakano, R. S. Allison, and I. P. Howard (2012) published very similar studies using the motion aftereffect to probe the way in which motion through depth is computed. Here, we compare and contrast the findings of these two studies and incorporate their results with a brief follow-up experiment. Taken together, the results leave no doubt that the human visual system incorporates a mechanism that is uniquely sensitive to the difference in velocity signals between the two eyes, but--perhaps surprisingly--evidence for a neural representation of changes in binocular disparity over time remains elusive.