An experimental criterion for consistency in interpolation of partly occluded contours

We develop an experimental measure of consistency of interpolation of partly occluded contours based entirely on observers' interpolation performance. We first describe the measure, which is based on a two-probe task that compares an observer's interpolation settings at a particular location with vs. without the observer's own setting presented at a nearby location. We then report two experiments aimed at investigating the behavior of the measure. The first compares the proposed measure to the predictions of contour completion models. The second investigates its performance in the Poggendorff and related configurations. We find that consistency covaries with relatability and cocircularity (both interpreted in graded terms) and, sensibly, yields a low measure for interpolation in the Poggendorff configuration. We conclude that the proposed measure of consistency operationalizes an important aspect of what is meant by the "strength" of a partly occluded contour.