Real-world presence of the irradiation illusion in colonnades

Demonstrate empirically whether the irradiation size-contrast illusion occurs in real-life architectural contexts such as colonnades, affecting perceived column thickness (e.g., corner columns viewed against bright sky appearing thinner than interior columns).

Background

The common explanation for thicker corner columns invokes the irradiation illusion, where bright-on-dark elements appear larger than dark-on-bright, potentially making sky-backdropped corner columns seem thinner.

The paper notes a lack of in-situ empirical testing or documented cases supporting this effect in architectural contexts, and explicitly states that its existence in real settings remains unconfirmed.