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The Learning Tower illusion has been explained as a simple perspective illusion. I suggest that it is a variant of the Jastrow illusion, applied to perspective tilt, and that the original explanation is inconsistent with its own implicit assumptions and with the visual resolution of pictorial stimuli in general.

The anchoring theory of lightness perception (Gilchrist et al., Psychological Review 106 (1999) 795-834) has been described as one of the most successful approaches to lightness perception. Yet, not only does the original proposal contain serious gaps and inconsistencies, later expressions of the theory, which was never formally revised, seem to contradict the original claims while leaving the gaps unresolved. These problems call into question the theory's viability.

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Hammad et al.'s (2008) conclusions as to the basis of angle illusions on a picture's surface are not justified by their data, which cannot in principle differentiate between their proposal and the proposed alternatives.