From colour-changing fire trucks to ‘The Dress‘, many optical illusions have baffled the internet over the years.
Now, a scientist from Harvard Medical School has discovered an illusion that might be the strangest yet.
The deceptively simple illusion features nine dots on a plain dark purple background.
But are the dots blue or purple?
Viewers have been left divided on Reddit, where the illusion has received over 4,900 upvotes and more than 500 comments.
While some claim the dots are ‘definitely violet’, others are convinced ‘they’re all purple’.
One particularly confused commenter wrote: ‘My eyes are going crazy… I guess I’m not going to sleep now. Thanks for sharing.’
So, what colour do you think the dots are?
This bizarre optical illusion has divided the internet as social media users can’t agree whether the dots are purple or blue. So, what colour do you see?
On social media, commenters were bitterly divided over whether the dots were blue or purple.
However, some commenters pointed out an even stranger effect.
One viewer wrote: ‘Only one is purple to me, but it keeps moving around.’
‘My perception of the color changes depending on whether I’m focusing directly on the dot,’ another added.
And another joked: ‘How does the purple dot know to change to where my eyes are looking?’
Although this might seem strange, this is exactly how the illusion’s inventor, Dr Hinnerk Schulz-Hildebrandt, intended it to function.
In reality, all of the dots are a bold purple and placed on a blueish background.
But, by holding your phone about 30 cm from your face and looking at each dot in turn, only the dot at the centre of your current focus should appear to be purple.
According to the inventor of the illusion, the dots are purple on a blueish background. This set of illusions shows how only the dots or words currently at the centre of our vision will appear purple, while the others seem to become blue
In another variation, 360 purple dots are placed on the same blueish background.
By holding your phone about 10cm from your face and slowly moving it further away, you should see more and more dots changing from blue to purple as your area of focus expands.
In a final version, Dr Schulz-Hildenbrandt created a ‘vanishing poem’ using text in the same purple and blue combination.
Holding your phone close to your face and reading carefully, you should see the word you are currently reading turn purple while the rest of the text becomes blue and fades into the background.
Dr Schulz-Hildenbrandt describes this as a ‘fixation and distance-dependent colour illusion’.
He writes: ‘A pattern of purple objects on a blueish background appears only purple where the viewer looks directly at it. In the periphery, the perception shifts towards blue.’
This illusion works because of the unique way that our brains perceive purple.
In our eyes, we have light-sensitive cells called S-cones, M-cones, and L-cones, which are sensitive to blue, green, and red light.
This illusion works due to the same ‘colour contrast effect’ which makes ‘The Dress’ appear black and blue to some, or purple and gold to others
While some colours like green, yellow, and orange are assigned to a specific wavelength of light, purple isn’t found on a particular part of the visible light spectrum.
Purple is actually generated in the visual cortex of our brains when a combination of L-cones and S-cones are activated.
This makes purple a ‘fragile and unstable perception’, which is easily influenced by psychological factors or surrounding context.
That ‘colour contrast effect’ is the same reason that many classic optical illusions feature objects that appear to change colour.
For example, lighting and the colour of objects in the background can make objects that are really blue and black appear to be white and gold, just like the famous blue-black dress.
Additionally, due to the distribution of the different cone cells in the eye, it’s actually easier to see purple in the centre of our vision than at the periphery.
By placing purple dots on a similar blue background, our brains can only generate the correct purple colour for dots at the very centre of our attention.
That is why the dot you are looking at becomes purple, taking on its true colour, while the others fade to blue.
WHAT IS THE DELBOEUF ILLUSION?
The Delboeuf illusion is one type of visual illusion where a dot surrounded by a large ring is typically perceived to be smaller than the same-sized dot surrounded by a small ring.
This optical trick works because your brain perceives the dot in the context of the outer ring.
It was named after the Belgian philosopher and mathematician Joseph Remi Leopold Delboeuf (1831 – 1896), who created it in 1865.
The Delboeuf illusion is one type of visual illusion where a dot surrounded by a large ring is typically perceived to be smaller than the same-sized dot surrounded by a small ring
In terms of plate size, the theory goes that having a smaller plate tricks people into thinking they have more food.
However, new research suggests that when people are hungry, they are able to identify food portion accurately, no matter how it is served.
According to the researchers, this indicates that hunger stimulates stronger analytic processing that is not as easily fooled by the illusion.
However, the Delboeuf illusion is widely believed to work in other contexts.
This article was originally published by a www.dailymail.co.uk . Read the Original article here. .