Collection: Blindness and the visually deprived

Optical Illusions

Although we have 5 major senses, most of the information from our surroundings comes from the eyes, making sight a very important part of our lives. The eye contains many rods and cones and they gather information and send it to the visual processing part of the brain, the information is sent via electric signals. Optical illusions can be caused by our brain expecting to see something, and processing the eye's signals in a way that creates something that makes sense on one hand, but on further looking begins to make less sense.

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Optical illusions are often described as visual images that differ from reality - the eyes and brain 'sees' something that doesn't quite match the physical measurement of the image. Optical illusions can work in various ways, they can be images that are different from the objects that make them, they can be ones that come from the effects on the eyes and brain through excessive stimulation, and others where the eye and brain make unconscious inferences.

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Can you believe squares A and B are actually the same colour?

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Both are the same colour orange....

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It is hard for us to imagine something we can't see before us even if it is scientifically true, and we heavily use our eyesight as proof of the truth. But with optical illusions... it is clear that our sight isn't always trustworthy...

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Are the vertical lines the same length?...(yes they are...)

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Are the middle circles both the same size?

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Which inner square is largest? ...(spoiler: both are the same size)

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Does this still image appear to be moving...?

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An optical illusion happens because the different parts of the eye process images and colours at different speeds, this sometimes means that false images are sent to the brain. The brain receives this information but actually, the eye only sees some visual information at any given time, and our brain processes this and fills in the gaps to give the impression of continuous movement. This is highlighted in a television which actually shows a different image 25 times a second but our brain doesn't see the changes.

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Are the lines straight?

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Impossible Frame?

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The red lines are actually straight and parallel...

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Read this out aloud... are there any mistakes?

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Three lines make a...?

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What can you see?

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We often use our own past experiences to guess and assume things about images or new things we see. However, are we always right...?

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Does this still image appear to be moving...?

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There are many different types of illusion. Physical illusions are illusions where something has happened before the light reaches the eye, such as a rainbow. Physiological illusions are the effects on the brain by stimulation of a specific type such as brightness, colour and movement. Visual cognitive illusions are those that go against what we perceive as logic, and can continue to confuse us even when we know the trick.

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A lovely vase?

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Are the horizontal lines parallel?

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Scroll the page.... (It's a still image!)

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When read from close-up the image reads 'One', but as you move further away more is revealed.

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BLUE&BLACK OR WHITE&GOLD???

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Recently, on Thursday 26th February 2015, this photo of a seemingly normal dress went viral on the internet. 

The meme originated from a washed-out photograph of a dress posted on the social networking services Facebook and Tumblr—disputing whether the dress pictured was blue and black, or white and gold. In the first week after the surfacing of the image alone, more than 10 million tweets mentioned the dress.

Although it was confirmed that the dress actually was blue and black, the image prompted discussions surrounding the matter across various platforms, with users discussing their opinions on the colour- white & gold or blue & black

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About a week before the wedding of Scottish couple Grace and Keir Johnston, Grace's mother sent her a photograph of the dress she planned to wear to the wedding. The couple disagreed over the colour of the dress. They posted the image on Facebook, and their friends also disagreed over the colour; some saw it as white with gold lace while others saw it as blue with black lace.

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Which colour your eyes see is in fact a consequence of the way our eyes have evolved, and tells you important things about how your eyes work out colour in a world lit by sunlight.

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The problem is that the brain has to avoid seeing the colour of the light reflecting off an object, and just see the colour of the object itself. If it sees a white shirt bathed in yellow sun, for instance, it needs to subtract the yellowness of the sun so that it can see the whiteness of the shirt – and it normally does.

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The same kind of system is found in cameras, and is called white balance. That allows the camera to do the same thing the brain does – deciding what should be white, within the image, and adjusting the colours accordingly.

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But the dress – blue and black, or white and gold – somehow confuses this system, it seems. Some brains look at the dress and attempt to discount the blue bitsomething like the ambient light of night time. Others try and get rid of the effect of the gold part, because the brain sees it as the colour of a sunny day, and sees the dress as blue and black.

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(BuzzFeed.com)

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People across the world got involved with the debate of "what colour is this dress", with people being seemingly split into two groups of 'blue&black' and 'white and gold'...

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That allows people to see both different colours, at different times, depending on the brightness of the room and the background of the page that the dress is presented on. Those things can encourage the brain either to see the ambient light as daylight-coloured or night-coloured.

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Those are the two different kinds of cells that are in your eyes, and allow the brain to see colours. Rods are more sensitive to light and are used to see shapes, but not colour. Cones are less sensitive to light, but are used to see colour. (Having lots more rods than cones is what leads to colour blindness.)

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But you’re also wired to see the colours one way or the other, according to some explanations of the dress. And it all depends on rods and cones.

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Having more of one or the other will lead you to be likely to see the dress as white or gold, or blue and black.

While it’s ultimately about what your brain decides it needs to do with the ambient light on the image, the types of cells in your eye will help decide.

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