Apparent Object Movement Produced by Head Movement under Water

It was predicted that due to the optical distortion produced.by wearing a facemask, the constancy of visual position would not be maintained under water, i. e., stationary objects should appear to move when the head is moved. Subjects made magnitude estimates of object movement in both air and water. Twice as much movement occurred in water as in air. Two underwater activities, head rotation while observing vertical stripes, and practice in hand-eye coordination, produced a small reduction in object movement. The results indicate that apparent object movement (loss of position constancy) should be added to the list of visual problems which confront the diver.