Is It Blue Light, Rather Than Darkness, That Makes Us Tired at Night?

By Veronique Greenwood | June 29, 2012 1:02 pm

spacing is important

The color you see is a perceptual trick of your brain: it is not, no matter what your preschool teacher told you, an inherent physical property of that red apple or green leaf. The truth is that colorful objects just happen to be reflecting wavelengths of light that our brains interpret as specific colors. Do we all see those reflected wavelengths the same way? Because the experience of color vision is impossible to share, we simply don’t know. It’s quite possible that they’re not. In fact, a certain subset of people may well see a hundred times as many colors of the rest of us, but, because of the essentially privateness of color vision, have never realized that they are different.

In a tour through recent research on the perception of color, Natalie Wolchover at Life’s Little Mysteries also turns up another weird insight to add to the long list of strange things about color vision: It could be the blueness of light around twilight that makes us calm, and the yellowness of light around dawn that wakes us up, rather than brightness and darkness:

In a study detailed in the May issue of the journal Animal Behavior, [researchers] found that changing the color (or wavelength) of ambient light has a much bigger impact on the day-night cycle of fish than changing the intensity of that light, suggesting that the dominance of blue light at night really is why living things feel more tired at that time (rather than the fact that it’s dark), and the dominance of yellow light in the morning is why we wake up then, rather than the fact that it’s lighter.

That suggests that maybe it’s yellow light, rather than bright light, per se, that we should be memorializing in verse. Note to modern Homers: perhaps that a “golden-fingered dawn” would be more appropriate than a rosy one.

Image courtesy of Robert J. Donovan / flickr

  • Kaviani

    I thought we did memorialize the dawn’s early light reasonably well.

  • James

    I’d heard that the exact opposite is the case; that blue light makes you more alert, and reduces melatonin levels. f.lux ( ) is based on this idea, and there exists other research that says blue light does precisely the opposite of calming you down.

  • Kea Giles

    Interesting. My husband has Asperger’s syndrome and he often talks about how blue some light is or how yellow or orange it is when it pretty much looks the same to me. He also claims that blue light has an affect on his mood. Do you know if there’s a study about color perception in folks with Asperger’s?

  • David_42

    Well, my personal experience says no. My heatpump’s indoor unit has a blue display and unless I shut it off I can’t sleep. An equally bright set of red LEDs on the humidifier aren’t a problem.

  • Kevin Folta

    It makes perfect sense because the central photoreceptors that condition the circadian clock in mammals and induce light-driven responses (opsins and cryptochromes) have well defined absorption spectra. Wavelengths that excite the molecule induce the response. Opsins work best in green-yellow and cryptochromes in blue.

  • Ron

    I find it very poetic

  • Greg

    Is it possible that fish might react to colours in a different way to humans?

  • Stan Broflowski

    This is exactly backwards. It is the bluer light that stimulates the retina to indicate daytime and promote wakefulness.

    If yellow light were to make you awake, campfires would be circles of insomnia. That could not be farther from the truth.

  • Ken Crepeau

    Maybe a correlation between night people versus morning people and how they perceive the colors would shed some light on the differences

  • Bull Shirt

    Some animals are active at night. They wake up because they are tired?

    The color of a red apple or green leaf is an inherent physical property of those objects.

  • Henry Miller

    This is interesting. I know that blue is a very soothing and tranquil color and makes us feel relaxed. This is why many doctors and dentists surgeries are painted blue. Yellow makes a person cheery and bright. Even schools are usually painted yellow, because it stands for joy, happiness, optimism, idealism, imagination, hope, sunshine, summer, gold and philosophy.


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