Staring at this "black hole", it will become bigger: Is it broken?

Author:Institute of Physics of the Ch Time:2022.06.29

Image source: Original Thesis

"Look again, look at you!"

Written article | chestnut

Audit | Erqi

Staring at this black hole, do you feel that it is constantly getting bigger? It seemed like a monster's mouth slowly opened, as if it was about to suck people into a bottomless abyss.

In fact, this is just a static picture, and every pixel above has not changed the color. However, you don't have to doubt your eyes, because strictly speaking, it is not them to deceive you.

After all, the eyes are just a light sensor, providing a signal for the brain. The important thing is that after the brain receives the signal of the sensor, it will be translated in its own way. The entire world in our cognition is made by the brain to help us.

In other words, you will have the illusion of "darkness spread". The key is not what you see, but the brain thinks what you see. Recently, Professor Bruno Laeng and his colleagues of Oslo University in Oslo, Norwegian, found that when people stared at the black hole in the center of the picture, the brain would think that people were moving towards a dark environment.

Looking at it, the pupils expanded

Generally speaking, when we enter the environment with sufficient light, the pupils will shrink to avoid receiving too much light. Conversely, if we walk from a bright place to a dark space, our pupils will become larger. This is to capture more light as much as possible.

So, if the light conditions in the environment do not change, will the pupils of a healthy person have no reason to enlarge or shrink?

"Expansion of the black holes" visited the wrongdoing map, giving scientists an opportunity to answer this question. Because this is an illusion of high dynamics containing light and dark changes. The research team recruited 50 adult men and women with normal vision, not only to investigate how strong the "black hole" expanded by these people when looking at the pictures, but also using the eye movement instrument to detect the diameter of the pupil. Large or small.

Image source: Original Thesis

It is just that in this experiment, the "black hole" map watched by the subject is not only the white background, but also many "black holes" maps of other color backgrounds.

The results of the subjective questionnaire showed that 43 of the 50 people reported that they saw the big scene of "black holes"; and the other 7 people felt that the "black hole" did not expand much, and some did not see the expansion at all.

The pupil data shows that when people stare at the "black hole", the diameter of the pupil will increase over time: when watching the "black hole" 0.5 seconds, the subject's pupil diameter is about 4.1 mm, and the "black hole" is watching the "black hole". After 8 seconds, their pupils have an average diameter of about 4.9 mm.

In addition, the background color in the picture is different, and the pupils of the observer are different. When the "black hole" is placed on the red/purple red background, the pupils are most obvious.

Overall, while people subjectively felt the expansion of the black hole, their pupils were also expanding. In addition, the more intense the subject of the "black hole spread", the larger the pupil expansion. Scientists speculate that maybe humans are not based on the actual light to regulate the size of the pupils, but to decide to magnify or reduce their pupils based on the perception of light by the brain.

If this is the case, even if the light conditions do not change, as long as the brain thinks that the environment is becoming dark, it will issue an order to expand the pupil. This unconscious physiological phenomenon also reflects the mind's understanding of images.

Black bottom "white hole", "white hole" on some other color backgrounds (picture source: original thesis)

And when the research team processes the "black hole" picture of the white background and turns into a "white hole" with a black background, let people stare at it. ——The brain may think that people are walking towards a bright environment.

Why is the brain misunderstanding

Scientists believe that the reason why people have such an illusion is because the brain automatically predicts how the light conditions are about to change.

Professor Bruno Lang, who participated in this research, said that when the black oval shape appeared next to the shadow, it was likely to remind people of some familiar scenes, such as walking into a tunnel or a cave during the day. Under such circumstances, the brain can predict that the environment will become darker in the next moment, and then expand the pupils in advance as a compensation mechanism.

The prediction tool we use is called "Optic Flow", which refers to the instantaneous speed of pixel movement on the plane of space motion on the plane. For example, if someone holds the camera and takes a big step forward at the moment of pressing the shutter, we will see "dynamic" from his still photo. "Commonly composed.

From a static diagram, it can be seen that dynamics, because each pixel shows instantaneous speed (picture source: mpin/schorner)

This concept was first proposed by a psychologist named James J. Gibson in the 1940s. In nature, many animals may use "light flow" to judge the relative movement relationship between themselves and the environment, so as to make favorable decisions, avoid dangerous conditions such as collision, and help themselves survive.

By the 21st century, there are even many machine learning researchers that use light flow to develop the AI algorithm to allow them to complete the information blocked in some videos, such as watermarks (or mosaic); Pull out from the film and reveal the background. Picture source: Gao et al., 2020

For humans, if the brain calculates the light flow calculated by the "black hole" image, it is similar to the light flow calculated in the mind when entering the tunnel. To a large extent, this is not a bug (vulnerability), but a Feature (feature), which is a skill that is beneficial to survival in the long evolutionary process.

Maybe we can only feel that the brain is so easily cheated when facing the carefully designed visual perception map. So to blame those talented researchers. For example, "the continuous expansion of the black hole" is an image designed by a scholar called Kitagang Mingjia. He is a professor of psychology at the University of Japan and one of the authors of this new study.

In addition, he also created a more famous work, which is the "rotating snake" vision. Of course, this is not a moving picture.

Original thesis: