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.
TOP
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