Try it for yourself: are you also being sucked into a deep, black hole?

Have a look at the image below. Does it seem like the central black hole is expanding and you fall into a deep black hole? Then you are not alone. A new study shows that this optical illusion – which is new to science – is perceived by about 86 percent of people. And this one is so powerful, it’ll even make fun of your pupils.

The new optical illusion. Image: Laeng, Nabil, and Kitaoka

“This ‘expanding hole’ is a very dynamic illusion,” said researcher Bruno Laeng. “The shadow surrounding the central black hole creates a sense of forward motion, as if the observer is being sucked forward into a hole or tunnel.”

Optical illusion

Such optical illusions are not mere gimmicks with no scientific usefulness. Researchers in the field of psychosociology study them extensively to better understand the complex processes of our visual system. And the optical illusion scientists now present in a new study proves particularly good at tricking our brains.

Experiments

In experiments, the researchers examined how the color of the hole (in addition to black also blue, cyan, green, magenta, red, yellow or white) and of the surrounding dots influence how strongly we respond to the illusion mentally and physiologically. On a large screen they presented variations of the ‘expanding hole’ to fifty women and men with normal eyesight. Then they asked them how strongly they perceived the illusion. While the participants stared at the image, the researchers measured their eye movements and the unconscious constriction and dilation of their pupils.

Findings

The illusion seemed most effective when the hole was black, the findings show. However, fourteen percent of the subjects did not notice any expansion of the black hole at all, while 20 percent did not notice it when the hole was colored. Among those who did observe an expansion, the power of the illusion differed considerably.

pupils

But perhaps the most interesting discovery is that the optical illusion is taking over our pupils. For example, the pupils of the participants appeared to dilate greatly when the hole was black, something that also happens when we end up in a really dark environment. With colored holes, the pupils constricted. Moreover, the more strongly someone perceived the illusion, the more the size of the pupils changed.

light

It means that our pupils react strongly to the optical illusion. “Using the illusion, we show that the pupil even adapts to imagined ‘light’,” concludes Laeng. “So it’s not just about how much physical light is actually perceived. The illusion of the expanding hole causes a corresponding dilation of the pupil, as would happen if the darkness really increased.”

So the illusion is powerful enough to trick the pupillary reflex in most of us. However, why 14 percent seem insensitive to the expanding black hole is still unknown. The study does show how very interesting and instructive optical illusions can be. And so research continues. “Future studies may reveal other physiological or physical changes that ‘shed light’ on how illusions work,” Laeng jokes.