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This illusion, new to science, is powerful enough to trick our reflexes – Neuroscience News

Summary: The new highly dynamic optical illusion of the “expanding hole” can be perceived by 86% of people. The illusion is so effective at tricking the brain that it causes pupil dilation as if we were entering a dark room.

Source: Borders

Take a look at this picture. Do you perceive the central black hole getting bigger, as if you are moving through a dark environment or falling into a hole?

If so, you’re not alone: ​​a new study shows that this “expanding hole” illusion, which is new to science, is seen by about 86% of people.

Dr Bruno Laeng, a professor in the Department of Psychology at the University of Oslo and first author of the study, said: “The ‘expanding hole’ is a highly dynamic illusion: the circular smear or shadow gradient of the central black hole evokes a marked impression of optical flow, as if the observer were heading towards a hole or a tunnel.

Optical illusions are not just gimmicks without scientific interest: researchers in the field of psychosociology study them to better understand the complex processes that our visual system uses to anticipate and make sense of the visual world – in much more circuitous than a photometer camera, which simply registers the amount of photon energy.

In the new study published in Frontiers of Human NeuroscienceLaeng and his colleagues show that the “expanding hole” illusion is so good at tricking our brains that it even causes a reflex to dilate the pupils to let in more light, as would happen if we really moved around in a dark area.

The pupillary reflex depends on perception, not necessarily on reality

“Here we show, based on the new ‘expanding hole’ illusion, that the pupil responds to how we perceive light – even if that ‘light’ is imaginary as in the illusion – and not only to the amount of light energy that actually enters the eye.

The expanding hole illusion causes a corresponding dilation of the pupil, as would occur if the darkness really increased,” Laeng said.

Laeng and his colleagues explored how the color of the hole (in addition to black: blue, cyan, green, magenta, red, yellow, or white) and surrounding dots affects how strongly we respond mentally and physiologically to the illusion.

On a screen, they presented variations of the “expanding hole” image to 50 women and men with normal vision, asking them to subjectively rate how well they perceived the illusion.

As the participants watched the image, the researchers measured their eye movements and the unconscious constrictions and dilations of their pupils.

As controls, participants received “blurred” versions of the expanding hole image, with equal luminance and color, but without any pattern.

This shows a large black hole surrounded by small black dots on a white background
The “expanding hole” is an illusion new to science, strong enough to cause the pupils of the human eye to dilate in anticipation of entering dark space. Credit: Laeng, Nabil and Kitaoka

The illusion appeared more effective when the hole was black. Fourteen percent of participants did not perceive illusory expansion when the hole was black, while 20% did not if the hole was in color. Among those who perceived an expansion, the subjective strength of the illusion differed markedly.

The researchers also found that the black holes promoted strong reflex dilations of the participants’ pupils, while the colored holes caused their pupils to constrict. For black holes, but not colored holes, the more individual participants subjectively rated their perception of the illusion, the more their pupil diameter tended to change.

Non-sensitive minority

Researchers don’t yet know why a minority seem insensitive to the “expanding hole” illusion. They also don’t know if other vertebrate species, or even non-vertebrate animals with camera eyes like octopuses, could perceive the same illusion as us.

“Our results show that the pupil dilation or contraction reflex is not a closed-loop mechanism, like a photocell opening a door, impervious to any information other than the actual amount of light stimulating the photoreceptor. On the contrary, the eye adapts to perceived and even imagined light, not simply to physical energy. Future studies may reveal other types of physiological or bodily changes that may ‘illuminate’ how illusions work,” Laeng concluded.

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About this visual neuroscience and optical illusion research news

Author: Press office
Source: Borders
Contact: Press Office – Borders
Image: The image is attributed to Laeng, Nabil and Kitaoka

Original research: Free access.
The pupil of the eye adapts to the holes that extend illusorilyby Laeng, Nabil and Kitaoka. Frontiers of Human Neuroscience


The pupil of the eye adapts to the holes that extend illusorily

Some static patterns evoke the perception of a central region or an illusory expanding “hole”.

We asked observers to rate the magnitudes of illusory motion or black hole expansion, and these predicted the degree of pupil dilation, measured with an eye tracker.

On the other hand, when the “holes” were colored (including white), i.e. emitted light, these patterns narrowed the pupils, but the subjective dilations were also weaker compared to black holes.

The rates of change in pupil diameters were significantly related to the phenomenology of illusory motion only with black holes.

These results can be considered in an account of present-perceiving visual illusions, where illusory movement and pupillary adjustments represent compensatory mechanisms to the perception of the next moment, based on shared experiences with the ecological regularities of light.

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