Purple, blue, or violet? Nine-dot optical illusion stumps netizens. What do you see? Photo inside

An optical illusion has divided the internet, as people can't agree on the colour they are seeing. The black and blue dress (or was it white and golden?) once stumped netizens, and the latest illusion is also confusing people about the colour they are seeing. A scientist from Harvard Medical School has created the illusion. It contains nine dots placed on a purplish background. The colour of the dots is a point of contention. Some people think the dots are blue, while others think they are either purple or violet. An even weirder observation is that some people say they see one dot purple; however, it keeps moving around (same here). Take a look and let us know what you see.

The nine-dot optical illusion is being heavily debated on Reddit. The caption of the post reads: "Are these dots blue or purple?" Nearly 5,000 users have reacted to the post, with hundreds more commenting on the optical illusion. Some see purple, some see violet, while others see blue. For some people, it changes depending on the point from which they are looking at it. A user wrote, "If I look directly at it, it's purple. If I look away at all it's blue." One commenter wrote, "My eyes are going crazy... I don't think I'll sleep tonight. Thank you for sharing this."

Why do the dots change colour in the optical illusion?

Meanwhile, the most intriguing observation is that the dots change colour depending on which one you are looking at. One user wrote, "Only one looks purple to me, but it keeps moving." Another added, "How does the purple dot I'm looking at know to change color?

The optical illusion was invented by Dr Hinnerk Schulz-Hildebrandt. So, what colour are the dots really? According to the creator, all the dots are solid purple on a blue-purple background. If you place the picture 30 cm away from your face, and look at each dot one by one, only the centre dot in your focus appears purple. Dr Schulz-Hildebrandt wrote, “A pattern of purple objects on a blue background appears purple only where the viewer focuses directly. At the periphery, perception shifts toward blue.”