A mind-bending optical illusion has gone viral on Twitter this week – and it’s seriously trippy.
The illusion, called the Perpetual Diamond, appears family simple, with a purple diamond on a grey background.
Looking closely, you'll notice that the diamond has very thin borders around it, which are crucial for the illusion.
Depending on the colours of the border, as well as the colour of the flashing background, the diamond appears to move in different directions.
Professor Arthur Shapiro, who developed the illusion, tweeted a GIF of it in action, writing: “The diamond remains fixed in one place but appears to move up, down, left, or, right.”
In a study published in the journal i-Perception , the researchers explained how the flashing border tricks our brain into thinking the diamond is moving.
They wrote: “The direction of motion is determined by the relative phases of the luminance modulation between the edge strips and the background."
For example, if the two top edges of the diamond flash ahead of the background, and the two bottom edges flash behind the background, the diamond appears to move upwards.
But if the two top edges of the diamond flash behind the background, and the two bottom edges flash ahead of it, the diamond appears to move downwards.
The researchers added: "The motion is generated entirely by changing contrast signals between the edge strips and background.”
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