You can watch the full video here.
Dr Julie Smith, a psychologist and TikToker who has her own practice in Ringwood, Hampshire, shared a video to her 2.8M followers, demonstrating how we can test out this illusion for ourselves.
The video begins in black and white with Dr. Smith sitting down in a garden with a big white cross on her forehead (you’ll understand why in a moment).
“You’re about to experience a negative after image,” she says.
“I’m going to trick your brain into seeing colour where there is none.”
Then, the video changes from being black and white to a saturated effect with Dr. Smith’s face appearing a bluey green colour - like a photo negative.
The cross colour has also change from white to black too.
Dr. Smith tells her followers to “keep focusing on the cross on my head.”
But how will this suddenly allow us to see colour that’s not there?
The psychologist explains that this is possible due to “overexposing receptors in your eyes to certain colours causes the brain to see inverted colours when the black and white image appears.”
In order for the illusion to be successful, Dr. Smith reminds people to keep looking at the cross on her forehand even when the image changes back to black and white.
The video has been viewed over 414,000 times, with over a thousand comments from people who tried out the optical illusion for themselves - with varying degrees of success.
One person said: “It did! But only for a split second.”
“Uh oh. I think my brain is broken,” another person wrote.
Someone else commented: “I see purple flowers, blue bench, green behind you and your shirt looks green.”
“It worked for me until I looked away from the cross on the play back,” a fourth person replied.
Try out the optical illusion for yourself to see whether it works for you.