This study investigates the factors underlying the Wundt curve in graphic design based on Berlyne’s reinterpretation. The paper presents the results of a psychophysical study in which Likability, Novelty, and Clarity of manipulated flyer design images were assessed by means of magnitude estimation. To connect these measurements into a unified framework, the authors propose a model based on the (inverted U-shaped) Wundt curve, where Likability exhibits a nonmonotonic trend and is determined by the product of perceived Clarity and Novelty. To test this hypothesis, subjective evaluations were conducted using flyer design images systematically varied along a feature-distance axis defined relative to typical designs, where the feature distance was computed using EfficientNet-B0. The results showed a Wundt-curve-shaped trend with a moderate fit to the idealized curve. The findings indicate that the product of Clarity and Novelty plays an important role in determining Likability and provide a basis for refining Wundt-curve-based models.