From the cigar nestled in the brickwork to ‘The Dress’, many optical illusions have left viewers around the world baffled over the years.
But the latest illusion is arguably one of the most bizarre yet.
Dr Dean Jackson, a biologist and BBC presenter, has shared a strange illusion on TikTok, which reveals a hidden man when rotated.
At the start of the video, a person with brown hair can be seen smiling at the camera.
However, as the image is rotated, you should eventually spot a second person – a man with a bushy moustache.
‘At what time does the man with a moustache appear in the clock for you?’ Dr Jackson asks.
The video has garnered huge interest across TikTok, with over 1.4 million views at the time of writing.
‘I blinked and he appeared from nowhere,’ one user commented, while another joked: ‘I didn’t see it, I blinked and then I got jump scared by it.’
MailOnline tested the optical illusion, and was able to spot the man with the moustache by the time the image was at the 6 o’clock position.
Many commenters agreed that the second man appeared at this time.
Taking to the comments, one user wrote: ‘1st time 6 o’clock, but the 2nd time it was 4 o’clock.’
Another added: ‘About ten seconds after 6, second time 4. I had to de focus my eyes to see it the first time.’
And one said: ‘Didn’t know what I was looking for until I blinked after 6 o’clock, and I was like wait! Where did he come from?’
Others agreed that they needed to blink or look away from the image before they were able to spot the second man.
‘Looked away when you said “what man” and there he was!’ one user wrote.
And one joked: ‘I was about to say “what man?” and then I blinked and he appeared!’
This isn’t the first time that Dr Jackson has baffled social media users with hidden images.
In another video, Dr Jackson presents a picture of a kookaburra sitting on a log.
He then reveals that there is actually a second animal hidden somewhere in the picture that only a few keen-eyed viewers can spot.
Dr Jackson describes this as an ‘experiment on reframing and reimagining based on a prior image.’
In the video, he says: ‘A kookaburra perched in a tree, I want to know how quickly you can reframe what you’ve just seen when we move on to another picture.
‘Lots of people who haven’t seen the first picture before see a very different animal here.’
WHAT IS THE CAFÉ WALL OPTICAL ILLUSION?
The café wall optical illusion was first described by Richard Gregory, professor of neuropsychology at the University of Bristol, in 1979.
When alternating columns of dark and light tiles are placed out of line vertically, they can create the illusion that the rows of horizontal lines taper at one end.
The effect depends on the presence of a visible line of gray mortar between the tiles.
The illusion was first observed when a member of Professor Gregory’s lab noticed an unusual visual effect created by the tiling pattern on the wall of a café at the bottom of St Michael’s Hill in Bristol.
The café, close to the university, was tiled with alternate rows of offset black and white tiles, with visible mortar lines in between.
Diagonal lines are perceived because of the way neurons in the brain interact.
Different types of neurons react to the perception of dark and light colours, and because of the placement of the dark and light tiles, different parts of the grout lines are dimmed or brightened in the retina.
Where there is a brightness contrast across the grout line, a small scale asymmetry occurs whereby half the dark and light tiles move toward each other forming small wedges.
These little wedges are then integrated into long wedges with the brain interpreting the grout line as a sloping line.
Professor Gregory’s findings surrounding the café wall illusion were first published in a 1979 edition of the journal Perception.
The café wall illusion has helped neuropsychologists study the way in which visual information is processed by the brain.
The illusion has also been used in graphic design and art applications, as well as architectural applications.
The effect is also known as the Munsterberg illusion, as it was previously reported in 1897 by Hugo Munsterberg who referred to it as the ‘shifted chequerboard figure.’
It has also been called the ‘illusion of kindergarten patterns’, because it was often seen in the weaving of kindergarten students.
