Pulfrich effect and the filling in of apparent motion

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This "filling in" of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.