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Kate Garraway causes a stir online after sharing 'unbelievable' and 'bizarre' optical illusion

Kate Garraway caused a stir online after sharing an 'unbelievable' and 'bizarre' optical illusion which left her fans baffled.

The Good Morning Britain presenter, 52, from Oxfordshire, posted an image of two blocks which appear to be totally different shades of grey piled on top of one another.

Yet when one finger is placed in between them, you can see that the two blocks are, in fact, the exact same colour and only appear different due to the effect of the darker and lighter shading across the middle.

Taking to Instagram yesterday, the I'm A Celebrity...Get Me Out Of Here star shared the illusion along with the caption: 'This caused a right stir in our house tonight...'

These two blocks appear to be totally different shades of grey piled on top of one another. But when one finger is placed in between them, you can see that the two blocks are, in fact, the exact same colour

Taking to Instagram yesterday, Kate Garraway shared the illusion along with the caption: 'This caused a right stir in our house tonight...'

Many of Kate's Instagram followers expressed how impressed they were with the 'incredible' optical illusion

One impressed person wrote: 'Oh my gosh, that's incredible. They eye can play such tricks on you.'

HOW DOES THE CORNSWEET ILLUSION WORK? 

People perceive the shade of 3D images in a certain way depending on the how the item is lit and the way shadows fall.

If the light is falling from the upper left and the two blocks appear tilted away from us, then we see the upper block as lit and the lower block in shadow, due to the light source coming from the upper left of the image. 

Combined with the contrasting shading in between the two blocks, our brain interprets the top block as dark and the bottom one as light. 

We perceive the upper square to be darker and the lower one to be lighter because that's  what our brains expect due to the other elements surrounding the grey. 

Another said: 'Wow! I can't stop doing it,' while a third added: 'This is unbelievable.'

'That's mad!' another individual wrote. 'You'd swear they were totally different colours.'

The image shared by the Smooth Radio host is called the Cornsweet illusion and was first documented by experimental psychologist Tom Cornsweet in the 1960s. 

Cornsweet, who is best known for his work in visual perception, noted that humans perceive colour and shade of 3D images in a certain way depending on how the items are lit and where shadows fall. 

We believe the upper square to be darker and the lower one to be lighter because that's what is logical and what our brains expect because of the other elements surrounding the grey. 

If the light is falling from the upper left and the two blocks appear tilted away from us, then we see the upper block as lit and the lower block in shadow, due to the light source coming from the upper left of the image. 

Combined with the contrasting shading in between the two blocks, our brain interprets the top block as dark and the bottom on as light.