iNTELLIGENCE

IQ solution to: The horizon moon illusion

There are mainly two explanations:

The apparent distance theory which emphasizes that the elevated moon's small apparent size is related to its perceived distance. It holds that the perceived distance to the moon at the horizon is greater than that to the moon at its zenith.

Recent theories postulate that the perceived size of the moon is the dominant cue to its distance. The accommodation of the eyes should increase while viewing the elevated moon. This is just the opposite of the apparent distance theory.

But which of these theories is correct?

Recently, a paper of Lloyd Kaufman and James H. Kaufman (PNAS 97(1) 2000, 500-505, PubMed, full text) confirmed the old hypothesis that the horizon moon is at a greater perceptual distance. They “conclude that the horizon moon is perceived as larger because the perceptual system treats it as though it is much farther away. Finally, we observe that recent explanations substitute perceived size for angular size as a cue to distance. Thus, they imply that perceptions cause perceptions.”

However, a theory is just a theory...

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