Why does this dark hole grow when we look at it? Study explains

One of the most studied perceptual phenomena in psychology and neuroscience, the illusion of expanding hole helps better understand how our brain processes visual information.

In the image, a still dark point seems to increase in size as we observed it, as if moving forward, and even as if we were falling into a black hole.

“The illusion of the expanding hole challenges the traditional views of the perception of movement, demonstrating how static images can evoke strong sensations of movement,” says a recently published article on the Arxiv pre-impression platform.

From psychophysical studies conducted in 2021, which showed that the iconic illusion produces not only a perceptual effect, but also the dilation of the pupil, A duo of researchers now proposes that illusion begins in the eye, then affecting the brain.

To test this hypothesis, Nasim Nematzadeh of the University of Flinders in Adelaide, Australia has created a computational model that simulates the functioning of retinal cells.

The operation of the expansion hole illusion


Within our retinas, we have some neurons specializing in receiving visual information (and transmitting it to the brain), called retina ganglion cells (RGCs in English).

They act basically as distinct filters of photography. When you look at the “expanding hole” standard, Some of these cells see the smaller dark center, while others perceive it greater.

When all these cells send their different “versions” to the brain at the same time, it becomes confusing. As some RGCs say the hole is small and others, that it is large, the brain interprets the difference as if the black hole has been growing and moving.

This is where Nasim’s Gaussian Difference (Dog) difference filter comes into play, which “sees” the same as our eye cells. He confirms that it is this “confusion” of signs that makes us see movement where it does not exist.

For this, Dog creates a blurred version of the image, taking two blurred layers, as the RGCs do. Adjusting the radius of the filter, the researchers realize that different cells interpret the image in different ways.

When these signs reach the visual cortex (part of the brain that processes vision), it occurs A process called lateral inhibition : Nerve cells inhibit or reduce the activity of their neighbors, generating the illusion of expansion.

Why is it important to know how this illusion works?


By reading the study, we can wonder why someone would spend time and resources to worry about optical illusions that, although fun, will not save lives or something like that.

However, behind this apparent simplicity, what is at stake are visual phenomena that, analyzed, can reveal important mechanisms of brain functioning and human perception.

Speaking to New Scientist, visual ecologist Jolyon Troscianko of the University of Exeter in the United Kingdom, who did not participate in the study, says that the study findings are useful for understanding nature’s standards.

“Zebra stripes and butterfly wings patterns, all these kinds of things that are often very poorly understood,” he exemplifies. But the main benefit is conceptual, because it increases our theoretical understanding about how these visual illusions work.

For the researcher, the explanations on this subject have so far been very vague and superficial, suggesting that the brain is confusing when interpreting a 2D image as a 3D hole.

Nematzadeh’s study, based on neural mechanisms and visual processing, is more accurate and at the same time simpler to understand and test, increasing our understanding of vision, he concludes.

Teachers explain how optical illusion can deceive vision

This content was originally published in why this dark hole grows when we look at it? Study explains on the website CNN Brazil.

Source: CNN Brasil

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