Centre-of-Mass Confounds Contribute to Familiar Size Stroop Effects with Boger and Firestone’s ‘Visual Anagrams’

‘Visual Anagrams’ are images that are recognised as one familiar object from one angle, but another object, when rotated (Geng et al., 2024). Boger and Firestone’s (2025) ingenious application of them uses examples that appear to be a large object from one angle, a small object at another. They report Familiar-Size Stroop Effects using those stimuli, claiming they must have reflected high-level recognition processes, as each visual anagram comprised identical visual features, just rotated. However, rotating visual anagrams introduces a range of subtle potential confounds. For example, in B&F’s stimuli, anagrams perceived as small objects had lower centres of mass (CoMs), those perceived as large objects, higher CoMs. CoM confounds might therefore account for those Stroop Effects. To assess this, a new experiment used stimuli with similar overall shapes (and CoM confounds) to B&F’s stimuli but designed to be less recognisable. The new experiment revealed Stroop effects, smaller than those observed by B&F, but consistent with a partial contribution to B&F’s findings. These results highlight important considerations when using visual anagrams in future research.