AI Helps Unlock Mystery of Optical Illusion That Creates Color from Black and White

Scientists have employed artificial intelligence to shed light on a centuries-old optical illusion where a black and white spinning disk appears to produce colors. This phenomenon, known as 'subjective color,' has long puzzled researchers studying human vision.

The Benham's Top Illusion

The most recognized example of this illusion is 'Benham's top,' a disk patterned in black and white that was once sold as a toy. When stationary, the disk's markings appear unremarkable. However, upon rotation, viewers perceive arcs of pale colors, such as red and blue, that are not physically present on the disk. Researchers have described this as one of the "remarkable mysteries of vision."

First developed in 1894 by British inventor Charles Benham, the spinning disc created the illusion of colored rings when rotated. This effect, also referred to as Fechner-Benham colors or pattern-induced flicker colors, quickly garnered the attention of scientists investigating how the eye and brain process color.

AI and Subjective Color

A new study aimed to uncover the mechanism behind subjective color. Scientists presented a black and white Benham's top to an AI model. This AI had been trained to predict subsequent images after viewing a variety of nature videos. Astonishingly, even though the input images contained no color information, faint colors appeared in the images predicted by the AI.

The colors generated by the AI varied depending on the colors of moving objects present in the training videos. The researchers suggest that this indicates a learned association between movement and color may contribute to the emergence of colors from black and white stimuli. This finding provides a new perspective on the classical mystery of how colors are perceived from a black-and-white spinning top.

The study's conclusions, published in the journal Scientific Reports, propose that subjective color might not be solely a retinal phenomenon. Instead, it may involve the brain's predictive functions, which use past experiences to anticipate future visual input. The framework presented offers a clear explanation for why colors appear on the arcs of Benham's top when conceptualized as moving objects.

Over the decades, experiments with the spinning disc have explored whether the colors originated in the retina, the visual cortex, or through interactions between different parts of the visual system. Previous research indicated that the perceived colors could change based on the speed and direction of rotation, offering insights into how the visual system processes the timing and phase of light signals.