Since the heated debates about the blue dress/grey dress on Twitter a few years ago, optical illusions have become very popular.
Steve Rathje is one of the specialists on the subject. On his account, he introduces himself as a psychology student, doing a PhD at Cambridge University. Passionate about science, he has already written a thesis and published several articles in prestigious media. And to pass the time, he has a TikTok account on which he has fun communicating about the functioning of the brain or psychology.
As Steve explains, this black and white image from Cardiff University will suddenly show its colours if you follow his instructions.
In the centre of the yellow and purple photo, which are not the actual colours of the original image, is a black dot that you have to stare at for 20 seconds without blinking.
The right colours are displayed!
After 20 seconds of staring, Steve offers you the black and white images again, and if you haven't moved, the blue of the sky and the green of the lawn should appear!
The phenomenon is simple: as Steve explains, staring at the central point makes the cone cells in your eyes work. This retinal persistence sends information to the brain, which transmits the opposite colours to our eyes!
In the colour palette, yellow is the opposite of blue. So after 20 seconds of fixation of the central point, our brain thinks that we are not looking at a yellow sky, but a blue one.
According to other researchers who have worked on this optical illusion, it is also our memory that is at work: our brain naturally knows that the sky is blue, that the grass is green, etc. It is therefore a mixture of what we know and what our brain analyses.
This article was translated from Gentside FR.