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Article History

Received: 2 July 2025

Accepted: 3 October 2025

First Online: 26 November 2025

Declarations

:

: All procedures were approved by the Institutional Review Board of the University of California, Irvine (IRB Protocol #3292).

: The authors declare no conflicts of interest.

: Informed consent was obtained from all individual participants included in the study.

: Not applicable.

: Visual illusions are fascinating because what we see diverges from reality. We explored whether there is a common visual illusion factor where people who are susceptible to some illusions are more likely to be susceptible to others. We measured 149 individuals’ performance across five common visual illusions, where each individual repeated each illusion 30 times. The results were of high resolution in that individual differences in illusion susceptibility could be accurately measured. Indeed, there is a single common factor—people who are susceptible to one illusion are more likely to be susceptible to another. This factor accounts for about of the variance, with the bulk of the variance unique to each illusion. We also present new plots for representing the quality of measurement and new methods for assessing uncertainty in these designs. Future questions revolve around how susceptibility to illusions relates to other cognitive abilities.