Volume 31 #4

Contents

1. Sensory motion aftereffects
2. Technique for studying the visual pursuit behavior in animals
3. Crowding-effect at the resolution limit of the visual system with various numbers of distractors
4. The dependence of visual acuity of ophthalmologically healthy persons on the macular thickness
5. Photobiomodulating effect of low-dose LED blue range (450 nm) radiation on mitochondrial activity
6. Evaluation of the effciency of channel development of proprioceptive feedback for myoelectric prostheses of the upper limb
7. Robust orthogonal linear regression on histogram in small-dimensional spaces
8. Recognition of projectively transformed planar gures. XI. A new methods for detecting projectively-invariant points of an oval

In psychophysical experiments we studied how surrounding (distractors) in uences stimulus recognition on the resolution limit of the visual system. The tests were Landolt rings. The distractors were similar Landolt rings or rings without gaps. The distance between the edges of the test and the additional objects varied from 0 to 1 diameters of the test. The observers’ task was to identify orientation of the test. Two experiments di ered by the number of distractors. In the rst experiment, only one distractor was added randomly to the left or right from the test. In the second experiment two distractors were located symmetrically around the test and had the same orientation. To determine the location of the test it was clearly visible point over test at a distance one and a half of the diameter. It was shown that two distractors worsened recognition of the test stronger than one distractor at the small separations, while an opposite tendency was observed at the large separations. Critical distances between tests and distractors, where there was a signi cant deterioration in perception, were the same in both experiments. Deterioration of perception at small separations can occur due to processing of the tests and distractors by the same receptive elds of neurons, which respond to the test in the best way. At large separations, the presence of one distractor is likely to divert attention from the test, which affects its identi cation.

Key words: recognition, crowding-effect, the Landolt ring, critical spacing, attention

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