The effects of the motion path and the length of the variable segment in the Poggendorff illusion without parallels

Previous studies have shown that small, but consistent, errors in an alignment task occur for oblique lines when the variable stimulus is a line segment but not when it is a dot. This discrepancy could have been due to the structure of the variable stimulus or its path of motion. These alternative hypotheses were tested in two experiments. The results indicated that motion path is irrelevant but that errors generally occur when extended line segments are adjusted and do not occur in the adjustment of very short line segments (“dots”).