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  • Humans can discern between 2.3 million colours - but try staring at this picture of us bursting

  • through the periodic table and focus on the green dot as we invert the colours. Don’t

  • stop staring there until I say. The light is travelling as a wave to your eye, and the

  • frequency of these wavelengths determines the perceived colour of everything in this

  • picture and around you. Humans have trichromatic vision, meaning we have three cone cells in

  • our retinas, each which are sensative to different wavelengths of light: blue, green or red.

  • Keep looking at the green dot and your brain will do something pretty neat. Did the image

  • change back to the original colour? Even though you were staring at a black and white image,

  • your brain perceived it to be in colour.

  • This phenomenon is known asafter imaging’ - after staring long enough at the brightly

  • coloured image, your cones slowly become fatigued and the supply of photopigment in the respective

  • cones becomes exhausted, which ultimately stops sending signals to the brain. In the

  • case of this illusion, the part of the photo where you see cyan, the green and blue cones

  • become tired and as a result there is increased activity in the unfatigued red cones. So when

  • the image switched to black and white we seered’ - cyan’s complementary colour.

  • Growing up, you likely learned about the primary colours red, yellow and blue - and their respective

  • complementary colours. But things are more complicated when you consider that the primary

  • colours in your printer are magenta, yellow and cyan, or that the screen youre watching

  • this on uses red, green and blue! These are different colour models, where RGB isadditive

  • meaning the mixing of different lights of colour create new colours - while the other

  • two aresubtractivemodels and absorb different wavelengths of light.

  • For example, when you hold a yellow object in real life (don’t use a lemon), it’s

  • actually absorbing every wavelength except yellow - that yellow light bounces back and

  • hits your eyes. But, when you look at this yellow object through your screen right now it’s actually

  • not yellow at all. Because your screen can only use red, green, and blue colours,

  • if you were to zoom in physically on anything yellow, it would actually be a combination

  • of red and green - and because the wavelength of yellow is between red and green, our brain

  • interprets this mix as yellow. (YELLOW SCREEN) So what youre seeing here is in fact not

  • yellow at all, but it’s stimulating a mix of your red and green cones, which your brain

  • interprets as yellow.

  • While plants come in a range of colours, the predominant colour is green, due to chlorophyll,

  • the energy absorbing pigment found in plants critical for photosynthesis. So, to effectively

  • attract pollinators such as bees, insects and birds, flowers have evolved to stand out

  • against green. It’s why you don’t see many green flowers. And flowering plants have

  • even evolved a suite of different colours to attract specific pollinators - known as

  • pollinator syndrome. Bird-pollinated flowers are mostly red, potentially to discourage

  • visits from bees, as their visual system is different than birds, making it hard from

  • them to discriminate between red and green.

  • Similarly, we all have our own favourite colours, but why? One theory suggests that colour preference

  • is gendered, where given the choice between cyan and red, men prefer cyan colours and

  • women prefer redder colours. Researchers hypothesize this preference has evolved from our hunter-gatherer

  • societies where women's visual systems were specialized to see ripe red berries against

  • green foliage. Another theory suggest that we like hues that we associate with pleasant

  • things - however, pleasant and unpleasant things are often the same colour - we love blue slurpee

  • but not blue mold.

  • Investigating these questions of colour had us thinking about links between science and

  • art. So in our latest AsapTHOUGHT we asked both artists and scientists about how they

  • view their world.

  • Check it out with the link in the description

  • and subscribe for more weekly science videos.

Humans can discern between 2.3 million colours - but try staring at this picture of us bursting

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B1 US yellow green colour brain staring image

Will This Trick Your Brain? (Color TEST)

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    Sh, Gang (Aaron) posted on 2016/08/16
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