Adapting to expansion increases perceived time-to-collision.

We used a tracking method to measure errors in estimating absolute time-to-collision caused by adapting to an expanding target. After adaptation, the estimated time-to-collision was longer than in the baseline condition. This was the case whether estimates were based on binocular information alone or monocular information alone. Estimates of time-to-collision were lengthened by 8-16% when based on binocular information alone, and by 18-25% when based on monocular information alone. These findings are consistent with a previous proposal that changing-size and changing-disparity information converge before the stage at which motion-in-depth signals are generated.