The mystery behind optical illusions lies in the eyes, not deep in the brain, according to new research.
A recent study from the University of Exeter disproved the idea that these brainwaves stem from complex psychological processes.
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The bar in the middle of the image is filled with only one shade of gray – and again, the left appears lighter and the right appears darker Credit: Dr. Jolyon Troscianko
Instead, they are simpler than scientists and philosophers first thought.
Visual illusions are caused by limitations in the way our eyes and visual neurons work, research has shown.
In a statement, sensory evolution expert and paper author Dr. Jolyon Troscianko said, “Our eyes send messages to the brain, causing neurons to fire faster or slower.
“However, there is a limit to the rate at which they can be activated, and previous research has not considered how this limit might affect the way we see color.”
READ MORE ABOUT OPTICAL ILLUSIONS
Take the optical illusion above, for example.
The bar in the middle of the image is filled with only one shade of gray.
And yet, it looks lighter on the left and darker on the right because of the gradient in the background.
“This blows up many long-held assumptions about how visual illusions work,” Troscianko said.
But if you’re able to see through the illusion, this latest research suggests you’re particularly hawkish.
Troscianko added that the findings also shed light on the popularity of high-definition televisions that have become the norm in 21st-century living rooms.
“Modern high dynamic range televisions produce bright white regions that are more than 10,000 times brighter than their darkest black, approaching the contrast levels of natural scenes,” explained Troscianko.
“How our eyes and brain can handle this contrast is a puzzle because tests show that the highest contrasts we humans can see on a single spatial scale is about 200:1.
“Even more confusing, the neurons that connect our eyes to the brain can only handle contrasts of about 10:1.
“Our model shows how neurons with such limited contrast bandwidth can combine their signals to allow us to see these huge contrasts, but the information is ‘compressed’ – resulting in visual illusions.
“The model shows how precisely our neurons have evolved to use every bit of capacity.
“For example, some neurons are sensitive to very small differences in gray levels at intermediate size scales, but are easily overwhelmed by high contrasts.
“Meanwhile, neurons that encode contrasts at larger or smaller scales are much less sensitive, but can operate over a much wider range of contrasts, yielding deep black-and-white differences.
“Ultimately this shows how a system with severely limited neural bandwidth and sensitivity can perceive contrasts greater than 10,000:1.”
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Categories: Optical Illusion
Source: newstars.edu.vn