ADAPTATION OF DIVERS TO DISTORTION OF SIZE AND DISTANCE UNDERWATER

This report describes a series of five experiments conducted during summer 1968 to examine adaptation of divers to size and distance distortion underwater. Visually perceived distortions of size and distance are produced by the diver's facemask which introduces an air-water interface between the eye and the object of regard. The effect of this interface is to decrease image distance by about one-fourth. Under these conditions objects are likely to be reported as closer or larger, or closer and larger than they actually are. Adaptation to distortions of size and distance were investigated by two techniques: (1) the method of adjustment where a diver adjusted the size of a horizontal line, set in the frontal plane at a fixed distance, to a length of 12 inches, (2) the method of estimation where the diver recorded his judgments of the size and distance of a series of targets which varied on these dimensions. Of the five experiments conducted in the Underwater Research Facility tank and swimming pool at UCLA and in the ocean, three were successful in demonstrating adaptation.