Lighting and Human Behavior
Lighting has the power to impact our mood and behavior.
Photo credit: Simon Berger
WHY DOES EXPOSURE TO LIGHT MATTER?
Have you ever lived through a dark and wet winter? How did that experience make you feel? Alternatively, how do you feel when you're inside a big box, warehouse-like store with bright, overhead lighting? Compare that to the feeling of having a candle lit dinner. They are vastly different. The term mood lighting exists for a reason and its important to understand why light exposure matters, and how it affects our physiology and regulates our mood.
Photo credit: Patrick Robert Doyle
It starts with sunlight; the catalyst for all life on earth. All living organisms require sunlight in order to exist. To be more specific, all living organisms require specific wavelengths of light provided by the sun in order to exist. We need light the same way we need nutritious food, clean water, and exercise.
It’s been millions of years since humans learned to control fire and over 140 years since Edison commercialized the incandescent electric light. While we now have light everywhere (24 hours a day if we so choose), it is only recently that scientists have begun to understand the impact light has on our physical well-being.
Given that we spend about 90% of our time under electric light (figure from before CoVid19), we can, and in some cases do, operate 24 hours a day. However, there is a cost to this.
HOW DOES LIGHT IMPACT OUR MOOD & BEHAVIOR?
Light influences our bodies in non-visual ways. Humans and animals have internal clocks that synchronize our bodies functions on a 24-hour cycle called the circadian rhythm. Our body responds to external cues in order to align physiological functions, such as alertness, sleep, and even digestion, to the solar day. Light is the most important external cue in this alignment.
There are light sensing cells in the retina, the innermost, light-sensitive layer of tissue of the eye. The retina is an extension of our brain and has three different photoreceptors: rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs). Rods facilitate peripheral vision and function mainly in dim light. Cones facilitate daytime vision and color perception. Photosensitive ganglion cells play a critical role in our circadian rhythm’s synchronistic relationship to natural and artificial light, sending information to various parts of the brain to trigger reactions downstream in the body.
The WELL Building Standard states that many physiological processes, including those linked to alertness, digestion, and sleep, are regulated, in part, by the signals involved in this “circadian” cycle. Light exposure is then significant because of the role it plays in sleep, alertness, and digestion. The Institute of Medicine reports that about 50-70 million US adults have chronic sleep or wakefulness disorder which is associated with an increased risk of diseases like diabetes, obesity, depression, heart attack, hypertension, and stroke. To maintain optimal circadian rhythms, the body requires periods of both brightness and darkness.
Sara Patterson, a graduate student in neuroscience at the University of Washington School of Medicine, says that photo entrainment is the process of how our internal biological clock (sleep/ wake cycle) reacts to the external light dark cycle of the sunlight and artificial light sources. As the sun rises and sets, the total amount of light changes; Patterson says this is something that has been studied a lot, but the color of the light changes as well and this is less studied. The receptors Patterson studies are part of our color vision circuit, which are not for seeing colors but rather for using the colors to tell the time of day. Neuroscientist Mathew Walker says lack of sleep, also known as circadian rhythm disruption, is likely a contributor to cancer, alzheimer, anxiety, depression, loss of productivity, dementia, and even infertility. The neuroscientist tells Terry Gross on WNYC’s radio show Fresh Air that “Every disease that is killing us in developed nations has causal and significant links to a lack of sleep.”
So what if we could work with technologies to create artificial lighting conditions for us to thrive? That is what industrial designer, lighting and biomimicry expert Sarah Morgan is doing. Morgan is working to bring sunlight inside and get our circadian rhythms back in gear, and using quantum dots to mimic the direct way which sunlight bounces outside. Quantum dots are tiny nanoparticles made from semiconductor materials; their size determines their colors which could be used to coat the inside of light bulbs or wall surfaces. Think of tunable paint that mimics the rise and fall of the sun, or tunable lighting. Morgan is exploring applications like coating the inside of the Mars spaceship in quantum dots, or using them in areas where you need to wake quickly and go back to sleep quickly, such as spaces for Doctors and first responders.
Commercial aircrafts have already begun to incorporate tunable lighting in their cabins. An airline may have mood lighting scenarios in the cabin for boarding, dining, and sunrises.
Similarly with lighting, airports can gradually adjust passengers who have just arrived at their destination to the schedule of their new location even before they leave the building. Last November, the New York Times published The Travel Industry’s New Fix for Jet Lag which states “Some airport lounges have installed special lighting to help passengers shift. Before their 17-hour flight to London from Perth, Qantas passengers in premium cabins can use the international transit lounge, which includes ‘body clock intervention light therapy’ in its bathrooms to increase alertness. The SAS premium lounge in Oslo has a ‘daylight booster zone’ that exposes fliers to artificial bright light.” Hotels are jumping on the circadian bandwagon as well.
Luxury business aircrafts could employ Soleil circadian rhythm based cabin lighting systems which “automatically adjusts the cabin lighting to aid in stimulating or suppressing the production of melatonin which can help synchronize a traveler's circadian rhythm to the time at their destination.”
Jay Neitz, professor and scientist at the UW Medicine Eye Institute, and a well-known color vision researcher, says cones responsible for color vision weren’t well understood, so scientists at UW Medicine have started figuring out different lighting solutions the might solve some of our problems. They see a future where office lights, bathrooms, and overhead lights would also be healthy for you; lighting that would be somewhat like sunshine is their goal. Ideally, the short wavelength blue light and longer wavelength yellow light (which mirror the sun’s colors at sunrise, midday, and sunset) would both be inside of white light, and these lights would switch between colors in a way that the cells that communicate with our circadian rhythm can see, but our conscious vision do not.
Companies like Ketra have developed lighting systems that dynamically transition from bright and energizing light to warm and cozy light and back again. Ketra’s solutions are great for new projects, however might prove expensive for consumers. Other options such as Philips Tunable White Wi-Fi LEDs allow you to switch from warm to cool lights with an app at a much lower price point. Users can set the lights to align with the task they have to perform at any given time, whether for work, play, or relaxation.
Photo credit: Karl JK Hedin
And finally, a conversation about lighting would not be complete without making note of American artist James Turrell who has been mastering, molding, and creating experiences with light for decades. With his celebrated Skyspaces such as ‘Meeting’ at MoMA PS.1, Turrell invites viewers to gaze upwards at an unobstructed view of the sky, which open during sunrise and sunset, allowing viewers to notice and appreciate the subtle shifts in the color of the sky, yet again exposing the power and gift of sunlight.
WHAT TO DO ABOUT IT
Here are a few recommendations for human centered light:
Turn on night shift/ mode on your mobile device so your screen can mimic the correct light temperature throughout the day.
Keep consistent wake and sleep times; darkness is just as important as light. Binge sleeping or deprivation is just like binging or deprivation in other parts of life.
When indoors, match your lighting to the task at hand. If you want to be alert, use lighting that mirrors the midday sun; the higher the color temperature the more blue light, select bulbs that are 3500 kelvin or higher. For winding down and getting ready to relax and later sleep, use bulbs that are a color temperature of 2700 kelvin or lower, and use less lighting or dim the lights. Alternatively you can use circadian tunable white light from Ketra or Philips.
Get outside! Spend more time in sunlight and nature reconnecting with your evolutionary relationship with the sun.