AI unravels 200-year-old optical mystery

The phenomenon involves the Benham's disk, first created in 1894 by British inventor Charles Benham as an optical device. It later became a toy and quickly attracted scientists interested in understanding how the eye and brain perceive color.

When the disk is stationary, it appears as an ordinary black-and-white pattern. But once it spins, viewers may begin to see colored arcs in red, blue and green, even though none of these colors are physically present on the disk.

The phenomenon, known as subjective color, has puzzled scientists for nearly two centuries.

How did AI help solve the mystery?

In a new study, a research team from Japan's National Institute for Basic Biology showed the disk to an artificial intelligence system trained to predict subsequent images after watching videos of natural scenes. Although the input images were entirely black and white, the AI predicted the appearance of faint colors.

The researchers found that the colors predicted by the AI changed depending on the colors of moving objects the system had encountered during training. This suggests that the brain may link motion and color, and that this association could explain why people perceive nonexistent colors when the disk spins.

The scientists now believe that the phenomenon may not originate solely in the retina, but could also be linked to the brain's ability to predict upcoming visual scenes based on previous experiences.

In simple terms, when the brain detects movement, it may anticipate seeing certain colors—even when those colors are not actually present.

The researchers said the findings suggest that subjective color is linked to the brain's ability to predict the future based on past experiences, offering a new explanation for a visual mystery that has challenged scientists for nearly 200 years.

The team hopes the findings will contribute to a deeper understanding of how visual perception and the brain's predictive processes work.