Optical illusion showing four friends drinking whisky leaves people mindblown as they can only spot three

The internet has found another mad optical illusion to obsess over - and this one involves an invisible person drinking from a tiny whisky bottle.

From the mad snap of the sitting women that always has us baffled, a 'second horse' only people with a high IQ can spot, and a photo where people are arguing over which building is closer - optical illusions can always drive us up the wall.

And this one of four pals has left people mind blown.

While the photo features four people drinking whisky, most people can only spot three of them.

Can you see them? (Reddit)

Well, at very first glance, you can only directly see one person.

The main feature of the image, a bloke is wearing a kilt, hat and raincoat, appearing to be on some kind of hike.

But he’s clinking a miniature whisky bottle in the middle as two other friends can be seen with their arms outstretched from outside the frame.

However, in a mind-boggling way, while you can instantly see three people’s arms and hands, there are four drinks in the centre.

And, as the photo gains traction on social media again after being posted to Reddit, it’s taking people a minute to realise where the fourth friend is.

Sorry, what fourth friend? (Getty Stock Image)

“I thought the backpack was actually a person in the background at first lol,” one user wrote.

As another admitted: “Lol. For a second I had thought it was a failed AI generated image.”

But, and here’s a hint, people have pointed out just why it works so well: “Not so much an optical illusion, and more simple effective camouflage.”

Yep, if you follow that fourth whisky bottle, a navy-gloved hand can be seen having slightly blended into the bloke’s kilt.

That's some serious camo (Reddit)

And if you go from there, you’ll release there’s a camouflage sleeved arm doing the whisky clink, impressively blending in with the background. Plus, if you look in the bottom left corner, you'll see the kilt of the camo-wearer.

“Camo really works,” one joked as a user responded: “Had I not read this comment, I'd still be looking at the picture.”

Some still needed a little help as they said: “I guess I'd be the worst person at undercover combat. Where is the camo!??!?”

Another wrote: “The one time camo actually works I had to zoom in to see it what even.”

While of course, one user made the standard joke that the fourth person is ‘John Cena’.