Light, like scent, is something we don’t necessarily think about all the time. What is there interesting about light that people might not always think about?

A little more than four years ago, Eris Lis, M.D., began writing a series of brilliant and informative posts on RPGs through the eyes of a medical professional. Following is the tenth of them, which appeared here on February 9, 2013. 

This week, Skirmisher released its new anthology of short stories, Sword of Kos: Hekaton. As one of the contributing authors, I was, of course, very eager to see the finished book. As I was looking through it, I noticed something: a lot of the stories made a real point of emphasizing and describing the light, or the lack thereof. Last week, I wrote a bit about the sense of smell and how it often gets neglected by storytellers, so I suppose that this week I may have been primed to make observations about other sensory modalities.

Light, like scent, is something we don’t necessarily think about all the time. I know, for example, that with my current gaming group, we spend a lot of time traipsing around abandoned tunnels and stony depths, and it’s only every few sessions that someone remembers to ask where the light is coming from (the answer, of course, is “from the torches,” but we don’t always remember that until after the monsters have seen our approaching glow from several hundred feet away). So I got to thinking, what is there interesting about light that people might not always think about?

As the old wisdom goes, no matter how obscure a question may seem, someone, somewhere, has published a paper on the topic. Let’s talk about how light affects health. Light has two basic effects for the human body and, for our purposes, presumably has much the same effects on other humanoids. First, light lets people see, which ought not to come as a shock. Light also has a lot of other effects on the brain, though, most of which have little to do with the same neural networks that process vision.

Let’s start with something simple: the sleep cycle, or the circadian (literally, “approximately day”) rhythm. Under ordinary circumstances, a human who lives in a place with a predictable light-dark cycle will awaken and grow tired at times reasonably appropriate to that light-dark cycle, such that they sleep for about eight hours out of every 24. If you were take a person and put them in an environment without a light-dark cycle, you’d find that their sleep cycle changed a tiny bit… the “day” for most people would tend to become 24.5 hours or longer instead of 24. Game implications: I’ve always wondered whether the dwarven cities under the mountains were synchronized with their above-ground human neighbours. If the dwarves’ cycles are half an hour off from the surface dwellers’, then their day and night would rotate around the human clock, much like the out-of-synch cycle of moon phases means that the full moon can fall at the beginning, middle, or end of the calendar month.

People tend to feel better in brighter light… within certain logical constraints, of course. Bright lights will keep people from sleeping. People trying to work later at night perform better with bright lights around. People are more prone to depression during months with less sunlight, and some of those people can be treated by brief exposure to bright light first thing in the morning and last thing at night. Game implications: I don’t think that anyone knows exactly how long an adventuring party has to remain in a dungeon before they start suffering symptoms of depression, but humans probably weren’t designed to live in lightless caves for months at a time. Light that hits the lower part of the human retina seems to have more of an effect on regulating sleep and mood that hits the upper part of the retina, meaning light streaming towards the eye from above has more of an effect on the brain than light coming from below. Game implications: honestly, I haven’t got a clue about that one, but it’s neat.

Blue light in particular has some interesting effects on the brain. Blue light seems to be the light which most powerfully suppresses melatonin, a chemical in the body which plays a role in regulating sleep. Compared to red and green light, blue light seems to have a more powerful antidepressant effect. Reducing the blue light that enters the eye doesn’t seem to cause depression, though; ophthalmologists who remove cataracts from the eye routinely replace the eye’s cloudy lens with an artificial lens that partially blocks blue light, and dozens of research studies have shown to change in rates of depression based on whether a blue-blocking or regular lens is inserted. An excess of blue light isn’t necessarily good for you, though. Nurses who work in neonatal intensive care units spend a lot of time around blue lights, which are used to treat babies with jaundice, and a number of studies have shown that when they spend too much time near the blue lights, the nurses can become irritable, nauseous, manic, and even suicidal. Game implications: personally, I wonder about all those angelic halls with their blue walls and crystals, and whether they might have unpleasant effects on humans.

So all that being said, I suppose that there isn't that much interesting to be said about light, from a gaming point of view. I can only regret that lasers don't fall within my sphere of expertise, because you can always find something to say about lasers.