This dataset contains raw behavioral responses of 29 participants (M = 29.38 years, SD = 5.52, 17 females). The experiment was aimed to test the strength of Ebbinghaus illusion. The independent variables were the size of Ebbinghaus inducers (small inducer, large inducer, no inducer) and the size of target circle (small, large). During the experiment, participants were asked to judge whether the comparison circle was larger or smaller than the test circle. Each row in the dataset represents one trial. Below is a description of the columns: 1. Block: Indicates the experimental condition (1: No inducer - Small target, 2: No inducer - Large target, 3: Small inducer - Small target, 4: Small inducer - Large target, 5: Large inducer - Small target, 6: Large inducer - Large target). 2. Inducer Size: Indicates the inducer size (No inducer, Small inducer, Large inducer) 3. Target Size: Indicates the target size (Small target, Large target). 4. Comparison Circle Size: The size of the comparison circle presented on the screen, measured in degrees of visual angle. 5. Accuracy: 1 for correct responses, 0 for incorrect responses. 6. Pressed Key: 'j' for smaller responses, 'k' for larger responses. 7. Labelled Key: Represents the proportion of larger responses (1 for larger, 0 for smaller). 8. Reaction Time: The time (in milliseconds) between the presentation of the comparison circle and the participant’s key press. 9. Distractor Sizes: The sizes of the seven distractor circles on the screen, measured in degrees of visual angle. 10. Distractor Average Size: The average size of the seven distractor circles. 11. Target Location: The coordinates of the target position in each trial.