Extrapolation of horizontal motion to linear targets of different orientation.

In a motion extrapolation task the subjects were asked to press a button at the moment of the imaginary impact between a concealed moving stimulus and a stationary target-line intersecting with the extension of motion trajectory. Horizontal motion of constant velocity was used. The target-line had two possible orientations: vertical and tilted at an angle of 30 degrees with respect to the moving stimulus trajectory. Four extrapolation distances subtending 4.5, 6.0, 7.5, and 9.0 degs of visual angle were used. The target-line was presented 2 s before the disappearance of the moving stimulus. Target-line position and orientation were chosen at random. Four out of five subjects were significantly faster in predicting the impact between the moving stimulus and the tilted target-line. The results are compared to data obtained in line-segment extrapolation experiments and the existence of a common mechanism for spatial extrapolation in static and dynamic conditions is discussed.