SOME EFFECTS OF Y-AXIS VIBRATION ON VISUAL ACUITY.

Four experiments were conducted to measure vernier visual acuity during sinusoidal vibration of the head in the y-axis side to side. In one half of each experiment peak acceleration amplitude was held constant at 1.0 Gy in the other half, displacement amplitude was held constant at 0.03 cm. Frequency was the main independent variable. Experiments I and II examined the effects of vibrating the head at frequencies ranging from 13 to 78 Hz. The combined results from these experiments showed that in both the constant acceleration and the constant displacement conditions acuity is a U-shaped function of frequency and has a minimum in the frequency range of 26 to 34 Hz. Experiment III examined the effects of vibrating the target, using procedures similar to those employed in Experiments I and II. Decrements in acuity due to target vibration were smaller than those due to head vibration under comparable conditions. Experiment IV also examined the effects of vibrating the head using procedures similar to those in Experiments I and II except that the orientation of the vernier target with respect to the axis of vibration was changed from perpendicular i.e., vertical to parallel, i.e., horizontal. No differences were found between the acuity scores produced by the vertically and horizontally oriented targets, for either the constant displacement or the constant acceleration condition. Author