Every day, we use our brain to solve problems, think before we act, and interpret the complex world around us. The nonstop biological activities in the various parts of our brain allow us to see color, objects, and a three-dimensional world. However, not everything we perceive is correct.
For instance, take a look at the image above. Does tile A seem to be darker than B? Though roughly 65% of Corona del Mar (CdM) students surveyed anonymously said yes, A and B are in fact the same shade of gray. The secret? A gray bar connects the two tiles, making it easier to see that they are actually the same:
Why? According to the checkershadow illusion’s creator, Edward H. Adelson, the brain initially sees the two tiles as the same shade of gray. However, since tile B is in the shadow, the brain makes the tile look lighter. Since the brain also knows that checkerboards have an alternating light and dark pattern, it factors the shadow in to maintain the pattern. Thus, the brain determines that B is lighter after a complex but erroneous process.
Another set of illusions tricks the brain into thinking that motion is present when it is not. Does the image below seem to be moving?
There are areas that appear to bulge out and roll in the above static image. Why does the brain perceive movement? Each of the “seeds” in the image has a dark edge and a light edge. According to motion-illusion expert Dr. Arthur Shapiro of American University, when the pattern goes from dark to light and back to dark again, “it triggers the motion detectors” in the brain’s visual cortex. Since the seeds have that pattern on their edges, the brain perceives motion even though it is not there.
“It was interesting how our brains can make a still picture look like a moving picture because of its shape and color,” said an anonymous student.
CdM’s morning announcements are an illusion. When one tunes into Trident TV, what one actually sees are pictures flashing at a high-speed (about 18 frames/second). The brain then processes the flashes and strings the images together, giving one the illusion of motion.
Is this next image a duck or a rabbit?
Both animals are present, and 91% of CdM students saw it also. This is an example of a bi-stable illusion. The viewer sees one of the animals first, and then changes his or her viewpoint to see the other animal. In other words, one cannot see a duck and a rabbit simultaneously. “I saw the duck first then had to tilt my head to see the rabbit,” said freshman Brenna Roberts.
The rabbit-duck illusion is also an example of an ambiguous image, an image that can be interpreted in two or more ways because there aren’t enough visual cues, such as color, for the brain to label it a certain object.
These types of illusions test one’s creativity as well. The more imaginative one is, the more likely one will be able to see other images in the same picture.
This last illusion will leave the brain confounded by color. Focus on the black dot for 20 seconds in the center of the neon-colored photo below, then quickly shift your glance to the same dot on the black-and-white image.
Did the building in the black-and-white photo appear fully colored momentarily? According to Yale psychologist Brian Scholl, when one stares at certain colors for a some time, the photoreceptors in the eye become fatigued. Then, when one shifts one’s eyes to a different place, (in this case the black-and-white photo) the complimentary colors show through because the original colors are unresponsive. The hues of blue, brown, and green in the afterimage are opposite to the color tones in the first picture.
“It is interesting how the eyes will still see color even though the image may not be the original color it was,” said an anonymous student.
In the end, the image that the brain forms about the world around you can be deceptive. Colors and shadows can manipulate the eyes into seeing a different reality.
“I guess you can say that our brain has a tough time comprehending things that are a lot to take in. The brain has to make stuff up to make things fit into our line of reason,” said a freshman survey taker. The world around us is always changing. Optical illusions remind us that seeing isn’t always believing.
Tactile Illusions: These types of illusions deceive your sense of touch. Some examples for you to try out at home include:
- Put one hand in a bucket of cold water and the other hand in a bucket of hot water and then wait for a minute. Then, put your hands both in a bucket of lukewarm water, and it will feel like the hand that was in cold water will feel hot, and the hand that was in hot water will feel cold.
- Cross your index and middle finger, and rub them along the bridge of your nose for about a minute. It will start to feel as if you have two noses.
- Lie on the floor belly down, and have someone hold your arms two feet off the ground for about a minute. Keep your head hanging, and your eyes closed. After a minute, have that person slowly lower your arms to the floor. It will feel as if your arms are going below your body.
Auditory Illusions: Sounds and pitches that deceive your sense of hearing. Some examples to look up on YouTube include:
- Shepherd’s Tone
- Binaural Beats
- Franssen Effect
- Octave Illusion
- Illusion discontinuity
- McGurk Effect
- Glissando Illusion