Evidence for curvilinear interpolation from dot alignment judgements

Visual interpolation between dots responsible for rectilinear versus curvil inear contour interpretation was examined with the psychophysical forced di rectional response (FDR) paradigm. Regular four-dot polygon segments, toget her with a target dot, were presented to the subjects for 150 ms. Subjects were required to indicate the direction of deviation of the target dot from the midpoint of the intermediate line segment. Crucial variables were the outer angle of the line segments and symmetry axis orientation of the polyg on segment. Logistic regression analyses showed that curvilinear interpolat ion occurred for angles up to 30 degrees, but emerged more pervasively unde r the vertical symmetry axis orientation for angles up to 60 degrees. (C) 1 999 Elsevier Science Ltd. All rights reserved.