Recognition of halftone, contour, and silhouette figures under conditions of their masking

Shape recognition of natural objects was studied under conditions of tachistoscopic (12 ms) presentation and different degree of noise-like ("rain drops") masking in 15 healthy subjects. Three set of figures were used: halftone, contour and silhouette. For all sets of figures, mean group data reveal a drop of the correct response probability with increase in masking. Recognition of contours was shown to be significantly better than that of halftone and silhouette figures, whereas halftone figures were recognized better than silhouettes. Possible neurophysiological mechanisms of the revealed phenomena and their functional implication are discussed.