Study of crowding effect for stimuli of low contrast and large size in the centre of vision field

Abstract

We present the results of psychophysical studies on the effect of additional images (distractors) for identification of test stimuli presented at the center of the visual field. As a test we used low contrast Landolt rings with size 1.1; 1.5 or 2.2 degre es. Distractors were Landolt rings or rings without discontinuities of the same size. Distractor would appear to the right or left of the ring in the region of 1 to 2 between the centers of the diameters of the test images. The task of the observer was in distinguishing the orientation of test Landolt rings. It is shown that the presentation of the same shape distractor degrades test recognition at a distance of up to 1,8 diameter of the Landolt test rings, which exceeds the interaction areas defined previously in the studies of the of crowding effect. Distractor in the form of a ring without gap degrades the perception on a minimum distance, in contact with the test. Errors in distinction of orientation of test Landolt rings were not accidental: observers have often pointed out the orientation of the distractor. The possible impact of integration features of images and attention on the outcome of experiments factor is discussed.