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The Moon Illusion

By Grant Ocean

Conclusion

        By means of the two new concepts, the visual field volume and the converging point, I have provided a new and improved explanation of the Moon illusion. Although I cannot claim that I have the final answer to the illusion, I can definitely claim that in comparison to the previous theories my answer is more comprehensive since it can explain more phenomena associated with the Moon illusion. Some researchers suggest that understanding the Moon illusion can shed light on a wide range of fields such as optics, physics, psychology, neuroscience, physiology, astronomy, and philosophy. If so, it is up to the readers who are specialized or have more knowledge in these areas to apply the new concepts and understandings.
        Richard Gregory suggests that it is better to limit 'illusion' to systematic visual and other sensed discrepancies from simple measurements with rulers, photometers, clocks, and so on. However, I would like to ask how would we explain the discrepancy between the measurement of an object done by a ruler against it and that done by a ruler at some distance from it? One is the measurement of the actual size of the object and another is the measurement of the perceived size. This discrepancy between actual size and perceived size is the foundation of linear perspective. On the other hand, size constancy is a discrepancy from the measurements of the perceived sizes of objects, or a discrepancy from linear perspective. According to Gregory's suggestion, we should call linear perspective and size constancy 'illusions'. If not, we cannot call the Moon illusion, the Ames Room illusion, or afterimage 'illusions' either because we are using the basic rules governing linear perspective and size constancy to perceive the horizon and zenith moons, the figures in the Ames Room, and projected afterimages.
        Some people might think that the discrepancy between the measured and perceived sizes may apply to the 2-D pictures and figures. My response is that there are multiple realities for a phenomenon depending on the frames of reference. For instance, when you drop a ball in a uniformly moving train, you would see the ball descend in a straight line; and a person standing outside the train would see the ball fall in a parabolic curve. The observation of the straight line made by the falling ball and the witness of the parabola made by the same falling ball are both true in reality; both of them represent what happens out there in the real world. The tenet is that the visual truth is relative and the reality depends on which frame of reference the observers use. If you and the other person met and told each other what you had observed, each of you would think the other had an illusion. Similarly, when you use the figures without the background as the frame of reference, you may consider the figures as distorted when they are put in a context of diagonal lines, wings, and different sizes and colors etc. On the other hand, when you use the figures with the background as the frame of reference, you may not be able to tell whether the figures are distorted and you may simply assume that they are exactly what they are supposed to look like without a second thought. For example, if you did not know the “true” measurements of the Müller-Lyer illusion and were told by someone that the two lines were the same length, you would think that that person had an illusion.
        The so-called distortion of the lines or size in an illusion is not due to the fact that our mind is deceived by the context and then misrepresents the original line, shape or size; contrarily, the so-called illusion is caused by the actual physical forces and follows rigid rules like a falling body following the rule of the gravitational law. Our brain has been thought to process the sensory information by interpreting it based on our assumptions about the world and our experience. It has been thought that sometimes we misinterpret the sensory stimuli and our senses deceive us into experiencing a stimulus pattern in a manner that is demonstrably incorrect. What we see has been believed to be an image created in our brain which is assumed to be different from the reality. As such these researchers and theorists have focused only on what misinterpretations our brain has done or what goes “wrong” with our perception, rather than investigating the principles and rules that govern our perceptions. Based on my own understandings and explanations, the perceptual illusions are viewed not as misinterpretation or distortion of the sensory information through subjectivity. The sensory inputs are accurate rather than inaccurate in cases of the shape and size illusions; and our mind is not playing tricks on us and it has no other choices but simply follows rigid principles and rules like all the other objects in the world. Suffice it to say that the perceptual illusions are truthful representation of the physical world; therefore, they are not really illusions as conventionally viewed. The implication of the new explanations of the perceptual illusions could be far-reaching. We are challenged to re-examine the long-held assumptions about our mental world, the nature of perception, and how our mind works. A new and better understanding of our perception and mind may come about as a result.


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The Moon Illusion Index
 

References


     Nanavati, S. (2009). A history and experimental analysis of the moon illusion. The New School Psychology Bulletin, Vol. 6, No. 1.
     Trehub, A. (1991). The Cognitive Brain. MIT Press.     

Related Information on the Web:

http://facstaff.uww.edu/mccreadd/index.html
http://www.lhup.edu/~dsimanek/3d/moonillu.htm
http://en.wikipedia.org/wiki/Moon_illusion
http://retina.anatomy.upenn.edu/~bart/scriptie.html
http://www.pnas.org/content/97/1/500.full
http://nspb.net/index.php/nspb/article/view/6/3

Appendix A


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