Red stimulates and induces appetite. You've probably heard this and other statements that are made regarding the effect of different colors on the body and mind. But do these claims support any scientific evidence? The physiological mechanisms that underlie human color vision have been studied for many years, but it is only recently that we have discovered and begun to understand the various ways that color affects not only our vision.
Like the ear, which also gives us a sense of balance, the eye has two functions. Light-sensitive cells - the cones in the back of the retina - send electrochemical signals directly to an area of the brain known as the visual cortex, where the visual images we see are formed. But now we know that some of the retinal ganglion cells respond to light by sending signals to the central region of the brain - the hypothalamus - which does not participate in the formation of visual images.
Light, but not to see
The hypothalamus is an important part of the brain responsible for the secretion of a number of hormones that control various aspects of the body's self-regulation, including temperature, sleep, hunger, and circadian rhythms. Exposure to light in the morning, particularly blue or green, results in the release of cortisol, which stimulates and wakes us up and also inhibits the release of melatonin. Late in the evening, as the blue light from sunlight diminishes, melatonin is released into the bloodstream, and we feel sleepy.
Retinal cells, which form the visual pathway between the eye and the non-conducting hypothalamus, are selectively sensitive to the shortwave (blue and green) colors of the visible spectrum. This means that there is a clearly established physiological mechanism through which color and light can influence mood, pulse, anxiety and impulsivity, among other things.
For example, this visual pathway to the hypothalamus is thought to be associated with seasonal affective disorder, mood swings that affect some people during the darker winter months and which are successfully treated with morning light.
There is also evidence that exposure to bright short wavelength light a few hours before bedtime can increase anxiety and affect sleep quality. Poor sleep quality is a known problem in modern society and leads to increased risk factors for obesity, diabetes and heart problems. It is believed that excessive use of smartphones and tablets in the late evening can affect sleep quality, because they emit enough blue and green at wavelengths that can inhibit melatonin release and prevent us from sleeping.
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Comprehending color
Next, in the first person - Stephen Westland, University of Leeds.
I lead the Experience Design Team at the University of Leeds, a dedicated light laboratory capable of assessing the effects of light on human behavior and psychology. This lighting system is unique in the UK: it can fill a room with colored light of a specific wavelength (rather than a mixture of red, green and blue, as is usually the case).
A recent study showed little effect of colored light on heart rate and blood pressure: red light seems to speed up the heartbeat, while blue light lowers it. The effect is small, but supported by 2015 work by Australian scientists.
In 2009, blue light bulbs were installed at the end of the platforms of the Yamanote Railroad Line in Tokyo to reduce suicide rates. And not without success: the number of suicides fell 74% at the stations where the blue lights were placed. Similar colored light bulbs were installed on the railway platforms at Gatwick Airport. These steps were taken based on the claim that blue light can make a person less impulsive and calmer, but there is little scientific evidence to support these claims. A three-year study (not yet published) by Nicholas Ciccone, a doctor in our group, shows that there is no solid evidence of the effect of colored color on impulsivity. Studies like these in our lab show the effects of color on creativity, student learning in classrooms, and sleep quality.
Obviously, light and color can affect us in ways that go beyond ordinary color vision. The discovery of a visual pathway that is not related to image formation has given new impetus to research that explores how we respond, both physiologically and psychologically, to the color around us. The increasing availability and use of colored lighting, driven by advances in LED technology, speaks for the need for serious research in this area. However, it is becoming increasingly difficult for people to distinguish between legendary data and research-based data.
Ilya Khel
