The threshold for the detection of disparity between points 10, 20 and 60 min apart was shown to depend on the number of intervening points. Even a single point bisecting the imaginary line both in depth and in visual angle often causes an approximate doubling of threshold and performance continues to deteriorate up to a point spacing that makes the line appear continuous. The effect is less pronounced if the intervening points are removed from the imaginary line joining the endpoints. Disparity detection in this kind of task involves local depth comparison of adjoining points and a more global mechanism.