The effect of concave and convex curve adaptation on the perceived expression of the real-face set derived from three MMI faces and the positional specificity of the effect (experiment 3). a , Psychometric functions from a naive subject under the following conditions. 0-f, no adaptation baseline (blue); cv-f-same, adaptation to the concave curve placed at the same location as the mouth position in the test faces (red solid); cx-f-same, adaptation to a convex curve placed at the same location as the mouth position in the test faces (green solid); cv-f-diff, adaptation to the concave curve placed 0.2° below the bottom edge of the test faces (or 0.9° below the mouth position) (red dashed); cx-f-diff, adaptation to the convex curve placed 0.2° below the bottom edge of the test faces (or 0.9° below the mouth position) (green dashed). b , Summary of all four subjects' data. The cv-f-same and cx-f-same conditions were compared, and the cv-f-diff and cx-f-diff conditions were compared, using the two-tailed paired t test.