Visual extrapolation of two converging nonintersecting line segments.

Fifty subjects were tested to determine the point of intersection between two converging line segments. The angle between the two nonintersecting line segments was 30 degrees. The orientation of the display as well as the distance between the line segments and the point of their intersection was varied. Two-dimensional normal distributions can be accepted to describe the results - the 50 estimates of the point of intersection for each of the five displays presented. The parameters of these distributions are influenced mainly by two factors characterizing the test line segments: (1) proximity to one of the main axes - vertical and horizontal, and (2) distance to the actual point of intersection. The possible mechanisms that might be involved in the estimation of the point of intersection between two converging line segments are discussed.