TYCHONIC ILLUSIONS: HARD VS. EASY
Reply to Harris and Pearson on Cognitive-Illusion

Abstract

Harris (1998) argues that a Tychonic illusion closely related to the one discussed in Margolis (1998a,b) is caused by the need to consider a situation in which there are two different frames. Pearson (1998) provides an argument against the conjecture that something related to blindsight is needed to account for that illusion. I reply to the two jointly as there is considerable overlap, arguing that the frames difficulty cannot account for persistent details of how people respond to Tycho's diagram, nor could the counterfactual motions that are implied by people's reactions be simultaneously both conscious and credible to the experts who in fact found them wholly credible for 400 years.

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References

• Harris, L. (1998), The Mars/sun Collision Illusion: motion is not visualizable in two different reference frames simultaneously PSYCOLOQUY 9 (34) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.33.cognitive-illusion.2.harris
• Kuhn, T. 1957. The Copernican Revolution (Harvard University Press)
• Margolis, H. (1998a) Tycho's Illusion: How It Lasted 400 Years, and What That Implies About Human Cognition PSYCOLOQUY 9 (32) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.32.cognitive-illusion.1.margolis
• Margolis, H. (1998b) Tycho's illusion and human cognition. Nature, 392, 857.
• Pearson, D. (1998), Imagery Need not be Blind to Fail PSYCOLOQUY 9 (34) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.34.cognitive-illusion.3.pearson