Perceptual contrast reduces the judgments of learning of small-font words and increases the judgments of learning of large-font words compared with the no-contrast conditions.

The font-size effect on judgments of learning (JOLs) refers to large-font words being rated as more memorable than small ones when required to predict memory performance during the study phase. This study examines perceptual contrast as the prerequisite for this font-size effect on JOLs and explores how perceptual contrast leads to this effect. In Experiment 1, perceptual contrast was achieved by inserting words with one font (e.g., 18 pt) into a series of words with another font (e.g., 70 pt) at a particular proportion (1:4). In Experiment 2, perceptual contrast was manipulated by presenting two different font words up and down in a pair. The results of both experiments showed that: (1) participants rated higher JOLs for large than small fonts under the contrast conditions, but the JOL difference between the two fonts was not significant under the no-contrast conditions; (2) the JOLs of small-font words under the contrast conditions was reduced compared with the no-contrast conditions, but the JOLs of large-font words under the contrast conditions was increased compared with the no-contrast conditions. These results indicated that perceptual contrast was the prerequisite for the font-size effect on JOLs. The reason for this effect is that, compared to no-contrast conditions, perceptual contrast reduces the JOLs of small-font words while increasing the JOLs of large-font words. This study may deepen researchers' understanding of the mechanism of the font-size effect on JOLs and help educators effectively guide students to learn.