A new optical illusion can trick most of us into thinking of a black hole.
The image is static, but researchers say it gives people a sense of darkness as if entering a void of light.
The illusory forward motion is a way of preparing us for a change of scenery. Our visual system can adjust quickly to potentially perilous conditions if we predict a change from brightness to darkness.
Just as glare can dazzle, being plunged into darkness is likely risky when navigating into the darkened environment.
Although, as in any illusion, this virtual expanding darkness is experienced at the cost of veridicality, since the observer is neither moving forward nor entering any dark space, such a cost is likely to be less severe than if there were no corrections.
The illusion of a hole expanding. Laeng et al. are in the front. It's a good thing. There is a Neurosci.
The first study looked at how the color of the hole affects our mental and physical responses.
A group of 50 participants with normal vision were presented with images of various colors on a screen. They were shown scrambled versions of the illusion with no pattern in light or color.
When the hole was black, the forward motion illusion was most effective. 86 percent of participants felt as though the darkness was headed towards them when the hole was this shade.
The eye movements of participants showed that they were looking at the black hole.
If the hole was not white, their pupils contracted a little.
The illusion that the pupils respond to light even if it is imaginary is based on the new "expanding hole" illusion.
If darkness really increased, the illusion of the expanding hole would cause a corresponding dilation of the pupils.
The authors are not sure why 14 percent of the group did not perceive an expansion when the hole was black. The strength of the illusion varied among those who saw it.
The people who felt the strongest illusion were those with the smallest pupils.
The results show that the pupils are not a closed-loop mechanism like a photocell opening a door.
The eye adjusts to perceived and even imagined light, not just physical energy.
There is a hypothesis for why the eye can do this. When the central region is black, our pupils are preparing us for a change.
The visual neural network predicts how information will change in the future, which creates an illusory hole in the central hole.
It would have taken milliseconds longer for the new visual information to reach higher processes in the brain if the brain didn't do this. We might not be able to navigate the darkness as efficiently if it took this long for our pupils to dilate.
The authors want to know if other animals are also tricked by the illusion to understand how the human visual system evolved.
The study was published in a journal.
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