[Solution of visuo-spatial tasks during masking]

The images of two fragments of simple geometrical figures (square, triangle, etc.) were successively presented to healthy adult subjects in the left and right visual fields with the interval of 20, 80 and 380 ms; the subjects had to compare them mentally and decide whether they formed a geometrical figure. The correctness of reaction was controlled by a computer which lightened on the screen the word "correct" or "error". The number of correct decisions was significantly greater in response to the stimuli, forming a regular figure and increased with the increase of interstimuli interval. At the interval of 120 ms, when no regular figure could be formed from two fragments, the number of correct decisions was greater if the stimuli were presented in the left visual field. The reaction time did not depend on the hemisphere to which information was addressed; it was less in response to the stimuli forming a regular figure, and became shorter with the increase of the interstimuli interval.