First it was #TheDress – a viral photo of a dress that appeared in different colours to different people – now it’s #AdelesFace.

The world wide web is a swirling pool of endless content, but every now and then something comes along that stops the masses in their tracks.

• #TheDress: we solve the colour mystery
• Forget #TheDress. Now it’s time for #TheShoe
• Resting bitch face: what is it and do you have it?

The latest oddity to captivate social media’s attention comes courtesy of British singer Adele, or her face at least.

This upside-down, sepia tone image of Adele – from the cover of her latest album 25 – was shared to Twitter and Instagram this week, receiving thousands of comments.

While the photo appears normal, when turned upside down it becomes clear Adele’s eyes and mouth have been flipped.

The big reveal has internet users labelling the image “horribly disturbing”, “crazy” and “creepy”.

However, this clever trick is nothing new. It was first identified in a 1980 paper by researcher Peter Thompson from York University.

In his paper, Thompson included an altered photo of former British Prime Minister Margaret Thatcher.

Similar to the Adele image, people were unable to see what was wrong with the portrait of Thatcher when it was upside down.

The Thatcher Illusion: at left, the unaltered photos, at right the altered photos. The top right photo appears normal.

This was even without the skilful and seamless image altering abilities afforded to us by Photoshop today.

Why so whacky?

According to Dr Carolyn Semmler, a senior lecturer in the School of Psychology at the University of Adelaide, the Thatcher effect (as it is now known) can explain why Adele looks so normal upside down and so bizarre right side up.

“Thompson effectively demonstrated that different orientation sensitivities of features in a face (eyes, lips, nose, etc) and configurations (relationship between features) may be responsible for the effect in humans,” Dr Semmler told The New Daily.

“[Adele and Thatcher] look normal when the face is inverted because the configural information is not easily extracted from the inverted face – we just don’t see the weirdness of the flipped eyes and mouth.

“However, when the face is the right side up it looks weird because the configural information we use for face processing is now dominant again, allowing us to see that there is something odd about the orientation of the eyes and mouth.

“In general, psychologists think that configural processing is the dominant type of processing engaged when viewing an upright face – but like all things in science this explanation is up for debate!”

Britney Spears looks far better when upside down. Photo: TurnYourPhone/Twitter

Completely trumped

A similar effect can be seen in another viral image, this time of American presidential candidate Donald Trump.

One keen-eyed Twitter user noticed a particular photo of Trump squinting during the GOP Debate in which his eyes were virtually indistinguishable from his mouth.

To test this theory, he replaced Trump’s eyes with his mouth using Photoshop. The resulting image was not remarkably different from the original.

⬅️ Original photo
➡️ Replaced eyes with mouth pic.twitter.com/kJGk9hH7ke

— Danny (@recordsANDradio) February 26, 2016

The jacket

Similar to “The Dress” before it, an image of a seemingly innocent Adidas jacket has divided opinion once again thanks to a trick of the eye.

“I hate to make a new blue/black white/gold dress meme but my friend has this jacket and she says it’s white and blue but I see black and brown please tell me what you see,” a user on blogging site Tumblr posted alongside a photo of the jacket.

The offending jacket. Photo: Tumblr

Whether you see a blue and white jacket or a black and brown jacket, the trick comes down to the ambient light in the image distorting our perception of the colours.

“It’s a colour context effect,” Dr Simon Cropper, senior lecturer at the University of Melbourne, told The New Daily in February 2015 of the dress effect.

“The surroundings and lighting presented with it will drastically change how it appears.”

What’s more, “difference in perception tends to occur on the blue spectrum because some people have more blue cones in their retinas than others”, Dr Cropper explained.

Regardless of the science behind these tricky images, one thing is certain: they’re fun to fool your friends with.