We have all seen optical illusions that change your sense of size, dimension, and proportions. They are created by your brain making assumptions, like filling in the blank areas when they don’t have all the information. How we perceive information is as important as the information itself. How do these illusions trick our brains?
The most common optical illusion is that of two lines of identical length, one with the arrows facing outward and the other with them facing inward. They appear to be of different sizes. This effect is extremely powerful, so much so that all other visual information is ignored.
Researchers at the University of London asked volunteers to search for a vertical line our of a field of other vertical lines, some tilted slightly, some with arrows pointing in, others with arrows pointing out. They were all just different enough to make finding the one they are looking for difficult.
Their eyes were constantly drawn to the longest appearing line, even if it wasn’t the vertical line. Chief researcher Dr. Michael Proulx says the reason is that, this is indicative of how our brain reflexively calculates size and length before anything else, and this process happens fast enough to guide where the eyes look, even if we consciously know that we need to be looking elsewhere.
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.”
These studies have led neurobiologist Dale Purves and his colleagues to a controversial new theory of how our brains perceive the visual world.
Sitting in a small, darkened room, Dale Purves stares at a computer screen that displays the image of two blocks stacked one on top of the other. The surface of the two blocks are different shades of gray, so he carefully adjusts the shading on two separate test patches until he finds two identical matches.
The fact is, Purves was wrong. The surfaces of the two blocks were identical (even though his colleagues also thought they were different). There was a covering of the figure’s center section, including the line joining the two blocks and the light and dark gradients. Ironically, the perceptual “wrongs” in this experiment, and many others exploring such visual illusions, have produced a remarkable scientific “right” –a radical new theory of how humans perceive the visual world.
What Purves and his staff have developed is a wholly empirical theory of vision, which believes that the brain processes visual information very differently than was previously thought. Neurobiologists had previously thought the brain was an organized mechanism, but after five years of meticulous experiments, Purves and his team have come to believe that vision is basically a reflex no different than the knee-jerk response produced when the doctor taps your knee with a rubber hammer. Certainly, these “vision reflexes” are more complex, says Purves, but like the knee-jerk, your visual sensations are encoded in already established visual circuitry that is simply waiting to be triggered.
The basic problem in vision is that the meaning of a light stimulus is inevitably ambiguous,says Purves. The light that reaches the eye is always a product of both the quality of the object’s surface and the quality of its illumination. So, it is impossible to know whether an object looks the shade or color that it does because of how it reflects light, or because of the nature of the light initially falling on it–or some combination of the two.
It goes back to our ancient ancestors and survival of the fittest.Those whose brains didn’t adapt for them to be able to distinguish shadows from holes in the ground did not survive. On the other hand, those whose visual perceptions generated behaviors that happened to work lived to reproduce, passing on their visual circuitry to offspring for further evolutionary refinement.
Says Purves, The visual part of the brain — and presumably the rest of the brain as well –works like a computer that doesn’t really ‘understand’ the rules of checkers. Nevertheless, it can develop a good game by simply changing its play according to the moves that worked well in a given situation in the past. We’ve had millions of years as a species, and a fair number of years as individuals, to perfect the neural networks triggered by visual stimuli. This very large amount of experience is what has made us so good at visualizing the world we live in, even though we never really see what’s there.
Purves added, People are obsessed with the idea that we human beings are not only different from other animals, but that our brains are different from our spinal cords, which clearly operate in a largely reflexive manner. The fact that our brain is not really so different from the spinal cord, except in degree, in no way demeans our humanity. In fact, our brains may be much easier to understand as engines of reflex association than as computers that analyze a scene and somehow tell an internal observer what it all means. In any case, our brains are still the most intricate and biologically effective structure in the known universe.
About the author:
Ron White is a memory expert
Sources:
109 Welcome from the future – Famous optical illusion reveals your brain’s hidden reflexes, say scientists: http://io9.com/5865964/famous-optical-illusion-reveals-your-brains-hidden-reflexes
Duke Magazine — Tricking the Eye or Trapping A Reflex? http://www.dukemagazine.duke.edu/alumni/dm29/purves.html
