Exposure duration affects the sensitivity of vernier acuity to target motion

Threshold vernier acuity was measured under different conditions of target movement and exposure duration. In the case of a simple two-line vernier target, image motion up to about 3 deg/sec had little effect upon threshold for a briefly exposed (150 msec) target, which is relatively poor even for a stationary stimulus, but produced a decrement in acuity for a continuously exposed stimulus. This finding was repeated in a second experiment, which used a centroid cue to vernier offset, and which compared the effects of horizontal and vertical target orientation. It is suggested that image motion and reduced exposure duration restrict the proportion of the light spread function that can be usefully sampled by the neural networks responsible for hyperacuity.