A bizarre optical illusion tricks your brain into seeing colours in a black and white spinning disk.
The phenomenon, which has baffled scientists for hundreds of years, fools viewers into thinking they can see colours such as red and blue when they are not present.
The most famous example of this is ‘Benham’s top’ – a disk painted in a black and white pattern which was initially sold as a toy.
When it is stationary, the opposing pigments appear unremarkable.
But when the top is spun, arcs of pale colour are visible at different places on the disk.
‘When a pattern drawn only in black and white is rotated, people sometimes perceive colours that are not actually present,’ researchers, from the National Institute for Basic Biology in Japan, said.
‘This phenomenon is known as “subjective colour” and has been studied for approximately 200 years as one of the remarkable mysteries of vision.’
So, can you see the different colours in the video below?
When Benham’s top is stationary, the black and white colours appear rather unremarkable. But when it is spun, colours such as red and blue can appear
As part of a new study, scientists wanted to work out the mechanism underlying this phenomenon.
They presented a black and white Benham’s top to an AI model that had been trained to predict ‘what kind of image will come next’ after viewing a range of nature videos.
Although the input images contained no colour information at all, faint colours appeared in the images predicted by the AI.
The artificially generated colours were found to change depending on the colours of moving objects contained in the video used to train the AI.
This indicates that learning a link between movement and colour may be one factor that enables colours to emerge from black and white simulations, the researchers explained.
‘This study suggests that subjective colour may not be a phenomenon completed solely within the retina, but may also be related to the brain’s function of predicting future visual input based on past experience,’ the team said.
‘By using AI, the study provides a new clue to the classical mystery of why colours are perceived from a black-and-white spinning top.’
The conclusion, published in the journal Scientific Reports, reads: ‘This framework provides a clear explanation for why colours appear on Benham’s top arcs when they are conceptualized as moving objects.’
For the study, researchers presented a black and white Benham’s top to an AI model that had been trained to predict ‘what kind of image will come next’ after viewing natural videos
This image plots the perceived hues that participants in a previous study reported. This phenomenon is known as ‘subjective colour’
Benham’s top was first developed in 1894 by British inventor Charles Benham, who created a black-and-white patterned spinning disc that produced the surprising illusion of coloured rings when rotated.
The effect became known as Fechner-Benham colours, or pattern-induced flicker colours, and quickly attracted the attention of scientists studying how the eye and brain perceive colour.
Over the following decades, researchers used the spinning disc in experiments investigating whether the colours were generated by the retina, the visual cortex, or interactions between different parts of the visual system.
Experiments found that the colours can change depending on the speed and direction of rotation, providing clues about how the visual system processes the timing and phase of light signals.
WHAT IS THE DELBOEUF ILLUSION?
The Delboeuf illusion is one type of visual illusion where a dot surrounded by a large ring is typically perceived to be smaller than the same-sized dot surrounded by a small ring.
This optical trick works because your brain perceives the dot in the context of the outer ring.
It was named after the Belgian philosopher and mathematician Joseph Remi Leopold Delboeuf (1831 – 1896), who created it in 1865.
The Delboeuf illusion is one type of visual illusion where a dot surrounded by a large ring is typically perceived to be smaller than the same-sized dot surrounded by a small ring
In terms of plate size, the theory goes that having a smaller plate tricks people into thinking they have more food.
However, new research suggests that when people are hungry, they are able to identify food portion accurately, no matter how it is served.
According to the researchers, this indicates that hunger stimulates stronger analytic processing that is not as easily fooled by the illusion.
However, the Delboeuf illusion is widely believed to work in other contexts.
