Can you spot the hidden color? Mind-bending illusion sparks online debate

From colour-changing fire trucks to ‘The Dress, numerous visual tricks have puzzled the online community for years.

Currently, a researcher from Harvard Medical School has uncovered an illusion that could be the most peculiar one so far.

The seemingly straightforward illusion displays nine dots against a dark purple backdrop.

But are the dots blue or violet?

Audience reactions have been split onReddit, where the illusion has received over 4,900 upvotes and more than 500 comments.

Some argue the dots are “clearly violet,” while others are certain “they are all purple.”

A particularly bewildered reader commented: “My eyes are going wild… I suppose I won’t be getting any sleep now. Thanks for posting.”

So, what colour do you think the dots are?

On online platforms, users were strongly split on whether the dots appeared blue or purple.

However, some commenters pointed out an even stranger effect.

A spectator commented: “Only one appears purple to me, yet it keeps shifting position.”

“My view of the color varies based on whether I’m looking directly at the dot,” another person said.

Another person quipped, “How does the purple dot know where my eyes are focused?”

Although this may appear unusual, this is precisely how the illusion’s creator, Dr Hinnerk Schulz-Hildebrandt, designed it to work.

In truth, every dot is a vibrant purple and positioned against a bluish backdrop.

However, by keeping your phone approximately 30 cm away from your face and focusing on each dot one by one, only the dot in the middle of your current attention should seem purple.

What hues are the spots?

As stated by the creator of the illusion, the dots appear purple against a bluish background.

However, only the dot that the viewer is currently focusing on should seem purple.

Our brains create the perception of purple when a combination of light-sensitive cells in the eye are stimulated.

This implies that the color purple is especially responsive to background hues, particularly in our side vision.

This causes the other dots to look blue when we are not paying attention to them.

In a different version, 360 purple dots are arranged on the same bluish background.

Keeping your phone approximately 10cm from your face and gradually moving it away, you will notice an increasing number of dots shifting from blue to purple as your field of vision broadens.

In a final version, Dr Schulz-Hildenbrandt created a ‘vanishing poem’ using text in the same purple and blue combination.

Holding your phone close to your face and reading carefully, you should see the word you are currently reading turn purple while the rest of the text becomes blue and fades into the background.

Dr Schulz-Hildenbrandt describes this as a ‘fixation and distance-dependent colour illusion’.

He writes: ‘A pattern of purple objects on a blueish background appears only purple where the viewer looks directly at it. In the periphery, the perception shifts towards blue.’

This trick functions due to the specific manner in which our brains interpret the color purple.

From our perspective, we possess light-sensitive cells known as S-cones, M-cones, and L-cones, which respond to blue, green, and red wavelengths of light.

Certain colors, such as green, yellow, and orange, correspond to specific wavelengths of light, whereas purple does not appear in a distinct section of the visible light spectrum.

Purple is created in the visual cortex of our brain when a mix of L-cones and S-cones are stimulated.

This renders purple as a ‘fragile and unstable perception,’ which is readily affected by psychological elements or environmental context.

The “color contrast effect” is the same phenomenon that causes many traditional optical illusions to display objects that seem to shift color.

For instance, lighting and the hues of objects in the background can cause real blue and black items to look like white and gold.just like the well-known blue-black dress.

Furthermore, because of how the various cone cells are arranged in the eye, it is actually simpler to perceive purple at the center of our visual field compared to the edges.

By using purple dots on a comparable blue background, our brains can only perceive the accurate purple color for the dots located right at the center of our focus.

That is why the dot you are observing turns purple, revealing its actual color, while the others shift to blue.

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