FUNCTIONAL DIFFERENCE BETWEEN CENTRAL VISION AND PERIPHERAL VISION IN MOTION PERCEPTION.

The lower and the upper thresholds of motion perception were measured along the horizontal and the vertical meridians of the retina in photooptic illuminance. The lower threshold was minimum at fovea and increased systematically with increase in the peripheral angle along either meridian. It was found that the minimum discriminable extent of movement, the displacement threshold, is no smaller in foveal vision and smaller in peripheral vision than acuity threshold. The upper threshold was determined by measuring the fusion length of a target moving sinusoidally to and fro. It was found that the upper threshold of motion perception increases systematically with increase in the peripheral angle along either meridian. From these results it was confirmed that foveal vision is superior in perceiving slow and small movement and peripheral vision is superior in perceiving fast movement.