People make freaky discovery after staring at dot for 15 seconds in optical illusion

You might find yourself rather baffled after looking at this optical illusion. It's no secret certain brainteasers are there to baffle you, whether there's an image you might struggle to find, or others which just go viral for hilarious reasons.

Now it's time to turn your attention to a Reddit post which recently confused around 3,500 members of the r/opticalillusions forum. In the caption, it wrote: "How does this work?" Meanwhile the photo above the woman's face read: "This is insane! Look at the dots on the nose for 15 seconds," before asking players to "now look here" at the blank image.

In the inverted high contrast image, it shows a woman smiling at the image with a very subtle dot on her nose. Your task is simple, look at the dot on her face, then glance at the plain white background in the image next to her.

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It's quite freaky because when you find you've done it and looked over, you can then see a face lurking on the white background.

Since the post was shared it racked up 3,500 likes and hundreds of comments. One said: "That was cool. Kinda jump scared me."

While another added: "Damn. Did not expect the ghost image to be in colour. Wow." A third pointed out: "You can also see her when you close your eyes." Others claimed the concept of the illusion was very cool.

So how does it work?

Known as a photoreceptor fatigue illusion, or negative afterimage illusion, this occurs when you stare at a colour for too long which causes the corresponding cone cells in your retina to become desensitised.

Basically when you shift your gaze to a white surface, which you have done in this case, your brain perceives the complementary colour of the original image because the fatigued cones are sending weaker signals, while the other cones send stronger cones.

Another example could be staring at a red target and then looking at white will then produce a cyan afterimage.

But sometimes you might not notice it as your eyes are constantly making tiny, involuntary movements which prevent any single set of cone cells from being overstimulated for an extended period.

And just remember, the fatigue typically lasts only for a short time, usually 10 to 30 seconds, after which the cones regain their sensitivity once the afterimage disappears.

Pretty clever right?