Perception Images Description and Discussion
Each image in this exercise is a target of your perceptual process, a point described in
your text. The following are some observations on each image (target). These are typical
reactions of viewers to the images, some of which you might have seen in earlier classes.
Images
Image I: Horizontal Lines Illusion
Image II: Vase-Face Illusion
Image III: Old Woman-Young Woman Illusion
Image IV: Prongs Illusion
Some Helpful Readings on Perception and Illusion
Image I: Horizontal Lines Illusion
The two horizontal lines are the same length. You can measure them on your monitor to
verify their length. Allow for some computer monitor distortion, especially with a curved
screen. This illusion is the easiest of the four to see.
This is the classic Müller-Lyer illusion published in 1889.1 The arrowheads distort our
perceptual process into believing that the horizontal line on the left is longer than the horizontal line on the right.
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Image II: Vase-Face Illusion
You likely have seen this image in an earlier class. It is a popular one for psychology
courses and some marketing courses that discuss perception and perceptual processes.
The image has both a vase and a face. You might need to view the image several
times to see both parts of it. If you did not see both images, return to the slide show and
try again. Vary your position in front of your monitor to try to see the different images.
You now begin to experience some parts of the perceptual process described in your
text. If you did not see both images, the one you did not see had not reached your recognition threshold—the point at which you can identify the target. If you eventually saw
both images, you also experienced the detection threshold of your perceptual process—
the point at which you noticed that the target changed.
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1
F. C. Müller-Lyer, Optische Urteilstäuschungen. Archive fuer Anatomie and Physiologie, 1889,
Supplement Volume, 263–270.
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Image III: Old Woman-Young Woman Illusion
Yes, there really is an old and young woman within the single image. The old woman image has a long chin and faces down from the center to screen left. The young woman has
her face turned away to the left. Her necklace is the mouth of the old woman image.
You can experience with this image the same parts of the perceptual process described for the Vase-Face Illusion. Both your recognition and detection thresholds could
have operated for this image.
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Image IV: Prongs Illusion
Viewers have the most difficulty with the Prongs Illusion. Your perceptual process shows
a dynamic element by alternating between two and three prongs. Jumping from one version to the other is a natural part of human perceptual processes.
The Prongs Illusion also triggers the two thresholds of your perceptual process. If you
saw alternating images, you experienced the movements between your detection and
recognition thresholds.
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Some Helpful Readings on Perception and Illusion
The following readings offer readable explanations of perceptual processes and illusions.
Use these sources to gain a better understanding of human perceptual processes and why
you reacted as you did to this exercise.
Coren, S. and J. S. Girgus. 1978. Seeing Is Deceiving: The Psychology of Visual
Illusions. Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers.
Gregory, R. L., and E. H. Gombrich. Illusion in Nature and Art. Duckworth
Robinson, J. O. 1998. The Psychology of Visual Illusion. Mineola, NY: Dover
Publications, Inc. Originally published in 1972 by Hutchinson & Co.
(Publishers) Ltd., England.
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