The effects of a moving line of light on the luminance threshold of a stationary target in its path have been compared for continuous and interrupted movement with three luminances of the moving line (2.0 to 0.023 ft-L), four speeds (17° to 170°/sec), and four widths of interruption of movement about the target position (0.13° to 3.43°). For both the continuous and interrupted movement the target threshold generally varied (a) with the luminance of the line divided by its speed, and (b) with the temporal interval between the presentation of the target and the arrival of the moving line at the target position. At short temporal intervals the rise in threshold with increasing luminance of the line was much greater than at long intervals. Although there were no substantial changes in the slopes of the functions, the point of maximum threshold rise was a function of speed. Both inhibitory and facilitative effects were magnified with very small interruptions of movement but decreased with larger interruptions.
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