You’ve seen the illusions, where two straight lines are of equal length, but the arrows at the ends point in opposite directions, which makes your mind believe the lines are of two different lengths. What about the photo where two people are looking at each other, but the area between them can either be in the background, or a vase in the foreground? These optical illusions are fun to look at and find different images in the same picture. But, how does your brain process these differences?
Next to your brain, your eyes are the most used part of the body. The retina, lens and cornea all work together to focus on a lot of information at one time, yet the eyes still rely on the brain to process this information. The eyes take the picture – the brain develops it.
What we see may not actually be what is. Huh? Well, our eyes see an image, which is can actually see only in two dimension, then sends that information on to the brain to interpret. The brain automatically compensates for what the eyes can’t see, just like when you have a “blind spot†– the brain fills in the blank areas. If the brain misreads the information supplied it can tell you it reads something other than what actually is there. Our “visual nervous system approximates color, shape and dimension.â€
That is why even people with perfect vision can still be fooled by an optical illusion – a picture that can have more than one meaning.
Our eyes need light in order to see. That is the reason we can’t see anything in pitch black. Light is reflected in the retina and forms an image, which is then sent to the brain. Actually, “sent†to the brain is not exactly correct, our eyes don’t “send†images to our brains, – they send signals. Images are constructed in our brains based on simple signals sent from the eyes. It is a complex, higher-order brain function, and a very large percentage of our brains are required to do nothing more than recognize what is in front of us. We see lines and motion, not images. Our brains interpret that as an attempt to recognize what the lines and motions represent.
What the brain “sees†when it processes the information sent from the eye is based on the interpretations from past experiences (memory), imagination and pattern recognition (association).
The term “visual†illusion is more appropriate than “optical†illusion because most effects have their basis in visual pathways and not from the optics of the eye. Optical illusions sound like our eyes are being tricked, when they actually are adapting to changes in vision, and these adaptations are hard-wired into our brains.
Each of our eyes has a region in which there are no receptors (rods or cones). This region is where the retinal ganglia exit the eye as the optic nerve. Our visual experiences do not typically include an awareness of the blind spots that result from the absence of rod and cone receptors in this region.
Researchers at the University of London asked participants in a study to search for a vertical line among a bunch of other slightly tilted lines. All of the lines had arrows on each end, some pointing out and some pointing in. All the lines were just different enough to make them appear to be of different lengths.
The eyes of the participants were consistently drawn to the line that appeared longest, even if it clearly wasn’t the vertical line. Dr. Michale Proulx, chief researchers, believes this indicates how our brain calculates length and size before anything else, and this happens so fast that the brain is able to guide the eyes where to look first; even though we consciously know we are supposed to be looking somewhere else.
Dr. Proulx explains: “The surprising difference here is that the perceived longer line not only captured their attention, but was even more distracting than the sudden appearance of something new as shown in prior research. This suggests that many visual illusions might be so effective because they tap into how the human brain reflexively processes information. If an illusion can capture attention in this way, then this suggests that the brain processes these visual clues rapidly and unconsciously. This also suggests that perhaps optical illusions represent what our brains like to see.”
About the author:
Ron White is a two-time U.S.A. Memory Champion and memory training expert. As a memory speaker he travels the world to speak before large groups or small company seminars, demonstrating his memory skills and teaching others how to improve their memory, and how important a good memory is in all phases of your life.
Sources:
The Secret Life of the Brain – Mind Illusions: http://www.pbs.org/wnet/brain/illusions/index.html
Memoriae.org – Illusions and How Your Brain Processes Them: http://www.memorise.org/brain-articles/illusions-brain-processes-00611.html
109 – Famous optical illusion reveals your brain’s hidden reflexes, say scientists: http://io9.com/5865964/famous-optical-illusion-reveals-your-brains-hidden-reflexes