VISUAL INSPECTION ALONE PRODUCES A DECREMENT IN THE HORIZONTAL-VERTICAL ILLUSION

Subjects inspected either inverted-T or L figures for 5 min. and then shortened the extended vertical lines of inverted-T figures in an atte mpt to make the vertical line equal in length to the horizontal line. Those who inspected inverted-T figures were more accurate on initial t rials than controls (who did not inspect figures), those who inspected L figures, or those who inspected inverted-T figures and made adjustm ents on the inspected figures. The results indicate that visual inspec tion alone can produce a decrease in the Horizontal-Vertical illusion and may account, in part, for changes in strategic factors which have been hypothesized to underlie illusion decrement.