Optical illusion triggers automatic brain reactions

In the laboratories of the University of Oslo, a seemingly ordinary image has caused a sensation among neuroscience researchers. A simple white background dotted with black dots, with a blurred black hole at the center, has revealed one of the most puzzling mysteries of our visual perception. This optical illusion is not only capable of deceiving our conscious brain, but it can even trick our most automatic reflexes. However, here is the most strange aspect: one out of five people remains completely insensitive to it, and scientists are unable to explain why this immunity exists.

Illusion creates a false perception of movement

When you fixate closely on the central black spot, your brain spontaneously interprets what you see as movement forward, as if you were heading toward the entrance of a dark tunnel. This illusory perception of movement triggers fascinating physiological reactions. Your pupils automatically dilate to let in more light, anticipating the coming darkness. This pupillary reflex, normally triggered only by actual changes in light, reveals how much our visual system can be influenced by purely imaginary perceptions.

Research highlights the illusion's unique power

Dr. Bruno Laeng, who leads this groundbreaking research, explains that this involuntary reaction demonstrates the exceptional power of this particular illusion. Unlike other optical illusions that only affect our conscious perception, this one manages to infiltrate the automatic mechanisms of our nervous system.

Variability in human perception

The most intriguing aspect of this discovery lies in the variability of human reactions. Out of the 50 participants tested, about 14% did not experience any effect with the black hole, and this percentage rises to 20% when the hole is colored. These individuals observe the same image as others, but their brains stubbornly refuse to create the illusion of movement. More disturbingly, these "non-receivers" show no pupillary reaction. Their eyes remain perfectly stable, as if they were looking at an ordinary static image. This complete absence of physiological response raises fundamental questions about the mechanisms of individual perception.

Pupil size reflects illusion intensity

The Norwegian researchers have also discovered a direct correlation between the intensity of the perceived illusion and the magnitude of the pupillary reaction. The more participants report seeing the hole expand spectacularly, the more their pupils dilate. This relationship suggests that the physiological response accurately reflects the subjective perceptual experience.

Pupils react to imagined light

Until now, scientists considered pupillary dilation as a purely automatic mechanism, functioning like "a photocell opening a door," according to Laeng's terms. The results, however, show that our pupils react not only to real light, but also to light that we perceive or even imagine. This discovery challenges the assumed boundary between objective perception and subjective interpretation of our environment.

Inverse experiment confirms the illusion's effect

The inverse experiment confirms this hypothesis: when researchers present a colored hole instead of a black hole, the participants' pupils contract, as if their eyes were adapting to a more intense light source. This opposite reaction proves that the brain actively processes illusory visual information as if it were a real environmental change.

Study published in neuroscience journal

These findings, published in the journal Frontiers in Human Neuroscience, open fascinating perspectives for understanding perceptual disorders and visual information processing. They suggest that our visual system functions more as a creative interpreter than as a simple passive receptor. The observed individual variability could also shed light on some aspects of neurological differences between individuals. Understanding why some people resist this particular illusion could reveal fundamental mechanisms of visual processing and open new therapeutic avenues.