Interpolating sampled contours in 3-D: Analyses of variability and bias

In two experiments, we examined how observers interpolated the missing parts of sampled, planar contours in 3-D space. We varied (1) contour type (linear or parabolic), (2) orientation of the plane containing the contour and (3) the number of points on a sampled contour. Interpolation performance was very accurate, comparable to results from Vernier tasks. Setting variability was highest along the line of sight and for the parabolic contour. Setting variability did not decrease with increasing number of points on either contour, suggesting that observers do not use all available, relevant information in this task.