(I am republishing a lot of ‘legacy content’ from our PLOS Neuroanthropology weblog, which has been taken down, along with many of the other founding PLOS Blogs. Some of these, I am putting up because I teach with them. If you have any requests, don’t hesitate to email me at: greg.downey @ mq (dot) edu (dot) au. I suspect many of the links in this piece will be broken, but I will endeavour to try to slowly rebuild this content. I originally published this on 7 November 2010. I have also included at the end some of the most substantial comments from the comment thread.

I’m also trying something totally new…)

This post is available as a podcast at Anchor.fm.

My ex-wife, along with her many other jobs – paid and unpaid – is the local director of a campus exchange program that brings US students to Wollongong, New South Wales.  Because of her background in outdoor education and adventure therapy, she does a great job taking visiting Yanks on weekend activities that get the students to see a side of life in Australia that they might not otherwise see.  From Mystery Bay on the South Coast, to Mount Guluga with an Aboriginal guide, to abseiling (rapeling) in the Blue Mountains, to surf lessons at Seven Mile Beach, I think she does a great job, and I frequently tag along to help and enjoy being reminded of the distinctiveness of my adopted home.

Invariably, either at the beach or in the Blue Mountains, at night, students will confront a clear, dark Australian sky, staggered at just how many stars fill the darkness from horizon to horizon. I’ve seen the US students – well, not all of them get into it – just stand, necks craned backwards, and stare.  What they thought was darkness was actually full of innumerable points of light.

I’m sympathetic because I had a similar experience one clear night in the Chapada Diamantina (the Diamond Plateau) in Brazil, when I couldn’t believe how, given real darkness, desert-like humidity, and clear, pollution-free air, the sky was crowded with sources of light, just smeared with stars.  For the first time, I felt like I understood the name, the ‘Milky Way,’ because I could see the uninterrupted blur toward the centre of our galaxy.

I was reminded of my experience with seeing stars, as if for the first time, and the reactions of the American students when I stumbled across the photos of Peter DiCampo (click here for Peter’s website), an American freelance photographer and former members of the Peace Corps who volunteered in the village of Voggu in rural Ghana.  His photo essay, Full Frame: Life without lights, is up at Global Post, an online American newspaper launched at the start of 2009.  His beautiful photos of life by flashlight, candle and gaslight, capture the atmosphere in this part of Ghana without electricity, and got me to thinking about artificial light and the way the sensory environment affects human development (additional photos at Peter’s personal website, including photos from darkness in Kurdistan).

Dark photos as activism

Peter’s photos are a form of social activism as well as both photojournalism and art.  As he describes, the images seek to convey concretely life in Voggu without focusing entirely on deprivation, drawing attention to the villagers’ condition without simply recapitulating familiar visual stereotypes in images (and I think he’s quite successful):

The villagers of Voggu are among the 1.6 billion people worldwide who live without electricity.

I had a simple plan: to photograph only with the light available, so that the reader can see only what the subjects are able to see….

I have no desire to contribute to a stereotypical view of Africa, presenting people as miserable and helpless — but I have every desire to use my photographs toward humanitarian means. How to reconcile the two?

The photographs – of night markets and kids reading the Qur’an and actors shooting a movie scene, as well as flashlight-lit portraits – don’t just bring us to a different geographical locale, but to a profoundly different sensory reality (as do the photos from Kurdistan that appear on his own website).  For most Americans and Australians, I suspect, living truly in the dark, with only tiny patches of light, would be a rarity.

Studies of nightglow, the light reflected back by humid or polluted atmosphere from ground level electric lighting, suggest that large portions of Europe, North America, and most urban areas are constantly swathed in low levels of ambient glow.  Nightglow effectively banishes night, shifting the daily cycle for every one, and every thing, living in these areas.

The effects of light at night

Navara and Nelson (2007), in the Journal of Pineal Research, review the diverse effects of artificial light on biological systems.  They discuss the extensive research on the negative effects of ambient nighttime light on animals, including disruptions to reproduction, migration, foraging behaviour and predation.  I won’t discuss these effects in any detail, but one of the sadder examples is that hatchling sea turtles often use the contrast between dark bush behind the beach and lighter horizon over the water to orient themselves when they are born.  Too much light on the inland horizon can confuse them so that they cannot find their way to water before predators get them.

Humans are also affected in a host of ways by nighttime light.  These light-derived condition are widespread, even pervasive; as Navara and Nelson (2007: 216) review: ‘In 2001, the percentage of the world’s population living under sky brightness higher than baseline levels was 62%, with the percentages of US and European populations exposed to brighter than normal skies lying at 99%’ (Navara and Nelson cite Cinzano and colleagues 2001 atlas of the night sky).  For some of these populations, true night is never experienced, for artificial light is consistently brighter than a full moon.

The increasing prevalence of high intensity artificial light that tends to be blue (rather than incandescent yellow) is especially troubling because light near this wavelength affects the pineal gland, which regulates melatonin production; long-term light exposure correlates with shrinkage of the pineal gland.  Just 39 minutes of incandescent light at night can cause melatonin synthesis to drop by 50% (Navara and Nelson 2007: 217).  As Korkmaz and colleagues (2009: 267) cite, elevated melatonin levels correlate with darkness and have been referred to as ‘the chemical expression of darkness.’  Altered or disrupted production of melatonin has a range of neuroendocrine effects on a range of bodily systems, including the metabolism of prolactin, glucocorticoids, adrenocorticotropic hormone, corticotrophin releasing factor and serotonin.  Long-term exposure to light at night can contribute to chronic sleep deficit, especially through the effects on melatonin, with ‘countless’ other effects, according to Navara and Nelson’s (2007: 217) review.

Over the long term, disruption of the light-dark cycle can affect body composition, contribute to obesity, negatively impact gut efficiency, and otherwise disrupt metabolism, especially the moderation of energy uptake.  These changes have been linked to diabetes, heart disease, and other metabolic problems.  Moreover, chronic exposure to low levels of light at night can lead to oxidative stress, which can damage immune cells and even contribute to higher incidence of cancer and rates of physiological aging (see Navara and Nelson 2007 for research review).

Because of the diverse endocrine disruptions caused by ambient night light, some health advocates argue for a decrease in the number of lights, for a modification of design, or for a shift to using lights which function less in the blue-violet part of the spectrum, which seem to cause the most biological disruption.

The dark in Ghana

But Peter’s photos also struck me because I was fascinated by the way that perception, too, might be altered.  When I emailed Peter to ask his permission to use his photo in this post, I asked him how he felt his perceptions were affected by living in an area without streetlights and neon signs and all the other electricity-based technologies that transform our experiences of night.  He wrote back:

As far as perception or vision – it was obvious to me that I was the clumsiest person in town. My Ghanaian friends, it seemed, could simply see in the dark. Maybe they couldn’t read a book, but they knew who was coming when he or she was still a great distance away, and they didn’t stumble as they walked around at night. I, however, wasn’t there long enough to adjust, apparently!

I also asked Peter how living with dark night affected him more generally, his state of mind and overall experience of the Ghanaian countryside.  His answer highlights a range of issues:

As far as state of mind – it’s hard to say if it was the lack of electricity, or the slowed-down pace of life there, or a combination of both – but the nights were incredibly relaxing, and sometimes almost spiritual. There were more stars in the sky than I’m used to seeing, certainly, and then just a pocket of lights here and there looking across the village. I slept earlier and easier there as well… days were often stressful, between the heat and the fact that I was a volunteer without much of a schedule, so I was often at a loss if I had nothing specific to do. But at night, things quieted down (often except for drumming in the distance), cooled down, and, without light, seemed to slow down as well…

Although the endocrine effects of nightglow are sobering, I just want to briefly discussone of the other issues that Peter highlights: the effect on vision, the shift in the pace of life and clear demarcation of night and day, the shift in ambient noise at night. Even though nightglow has infiltrated so many people’s lives, Peter’s photos ask us not only to reflect on those who do not have pervasive electrical lighting, but also the subtle ways that light might be affecting those of us who do.

What we can’t see because of light

The predominance of electric lighting actually affects what we can see in counter-intuitive ways.  Shut the lights off, and we don’t stop seeing; we see differently.

I first really paid attention to this when I was living in New Mexico, working as a door-to-door salesman to help pay for my university degree (yes, that’s a whole other story, for another day).  On the desert, I realized that I could see more without lights, even when driving (don’t worry, no humans or animals were harmed in these experiments).  With a headlight or flashlight, one’s field of vision only extends as far as the light; turn the light off, wait long enough, and the visual field opens up. In the ‘dark,’ I found I could see much further, and my peripheral vision improved, but a lot of detail disappeared, especially colour.

Artificial light shifts the quality of vision at night, allowing us to use our cones, which give us colour vision and are disproportionately concentrated in the fovea, or the focal area of the visual field.  In low light, the cones aren’t terribly useful, so we wind up depending on our rods, which are more sensitive in near darkness.  (Of course, in true, complete darkness, we can’t see anything.)  So, if you turn on a lantern or a flashlight, you’ll see colour and detail in the light field, but you will create a visual field defined by that light, an envelope of vision beyond which you can’t see.

Peter DiCampo’s photos of Ghana capture this so well, in part because the camera does not have the same versatility as our own eyes.  Whereas the eye adjusts as it moves away from light, becoming more sensitive, the photos are adjusted to make the brightly-lit areas appear normal, highlighting the way that artificial light creates bubbles of visibility.  But the point is that, at least to some degree, the bubble of light also helps make the sea of darkness around it appear darker.

One price for our bright nights, as the American students who marvel at the stars suggest, is that we are surprisingly unaware of what is above us at night.  People in my human evolution class are sometimes amazed by the fact that people thousands, even tens of thousands of years ago, were so aware of astronomical phenomena, but our ancestors may have been startled by how hard it is for us to see the sky at night. We should still be impressed by the accuracy and precision of their observations when they created architecture or petroglyphs which captured particular astronomic events (solstice, for example), but we also need to recognize that, for most of our existence, humans would have seen a very starry sky at night, and been much more aware of what was happening above them.

Astronomers have to work hard to find good places from which to observe the sky, in part, because we’ve made the atmosphere a soup of ambient light (see, for example, The night sky in the World).  They’ve been the most active in campaigning against light pollution for its negative impact on astronomy.

Adapting to the darkness

In fact, the human eye is versatile in a range of light levels, quickly adapting to variations in brightness by constricting or dilating the pupil.  Humans have poor night vision, like a lot of diurnal mammals, for a range of reasons: smaller eyes, pupils that don’t dilate as widely, a disproportionate amount of cones rather than rods in our eyes.

In addition, like most diurnal mammals, humans lack a tapetum lucidum, as do most primates. The tapetum lucidum is a layer of tissue lying within or behind the retina that reflects light back onto the eye’s photoreceptors, effectively boosting the intensity of the light signal so that they can see in low light. The arrangement does, however, apparently cause some degradation in the sharpness of the image and contributes to the way that nocturnal animals’ eyes often shine when exposed to bright light (anyone who’s ever been ‘spotlighting’ for animals has seen the eyes, more accurately, the tapetum lucidum, reflecting back at them).

The key to human night vision is rhodopsin, a pigment found in the rods of the eyes.  Under low light conditions, the cones in our eyes, which detect colour, are much less useful than the rods, which only see contrasts of light and dark (and, coincidentally, figure predominantly in peripheral vision, one of my other obsessions).

Rhodopsin, also known as ‘visual purple,’ however, photobleaches, splitting when it interacts with light to form retinal and opsin after it has absorbed a photon.  The rhodopsin gradually reforms over time, but this means that, for approximately a half-hour, people whose eyes are exposed to light have their rhodopsin depleted. Your eyes will steadily adjust after you shut off the lights, but you will not be back to your maximum sensitivity until all the rhodopsin reforms.

Even the habit of looking into lights, one that people can be trained to avoid, can decrease night vision; for example, at night savvy drivers don’t focus directly at on-coming headlights as their eyes will recover more slowly after the oncoming car has passed.  Vision, like other sensory systems, arises from a complex relation among a whole range of the body’s capacities, not just the eyes in isolation, as ecological psychologist James Gibson argued.  How you move your visual attention can affect the receptivity of your eyes and their ability to handle low light. Because I frequently have to walk around our farm at night (especially to track down our cats to get them in the hayshed), and we don’t have spotlights at the paddocks, I know that as soon as I leave the house, I need to avoid looking at lights if I want to be able to more quickly adapt to low light situations.

Over the long term, it’s not clear to me (and I’ve searched high and low for studies on this) whether there might actually be enduring adaptation for visual acuity in the dark or a type of phenotypic adjustment to high levels of light that makes it hard for those habitually in the halo of electric lights to see.  I suspect that there might be; the work of Anna Gislén and her colleagues (2003) on the visual adaptation of ‘sea gypsies,’ the Moken of Southeast Asia, suggests that there might be an adaptive shift in the ocular reflex.  In the case of Moken, Gislén found that individuals who foraged by swimming developed acute underwater vision by suppressing the automatic dilation reflex.  In the darker depths, their pupils remained wide, as if seeing in brighter light, which helped contend visually with the changes in the eyes’ refraction under water.  The adaptation was not intentional, nor were they really aware of the changes.

Likewise, some arguments about the predominance of myopia (‘near-sightedness’) suggest that the condition may be an adaptation to the over-use of vision at short range.  If, in fact, some people’s eyes adjust to too much short range use (and a lack of opportunities to gaze further afield at the horizon), the condition would be a kind of adaptation to the built environment, but also simply to the pattern of use.  It’s not just what you see, but how you look at it that might be affecting how well your eyes work.

The hard thing about studying human capacities like this is that Western populations, the ones we know the most about from psychological research, appear to be such outliers in a whole host of ways (as I discussed back in a review of Joseph Henrich and colleagues’ article about how ‘WEIRD’ subject pools skew our understanding of human nature).  Given the pervasiveness of technology like electric lights, it’s only when someone like Peter DiCampo brings us such startling demonstration of other life worlds do we even realize the extent of our potential difference.

Peter’s bio

Peter DiCampo is an American photographer who divides his time between Africa and the Americas. He launched his freelance career in 2007 while also serving as a Peace Corps volunteer in rural Ghana. Before living in Ghana, he was a staff photographer at The Telegraph in Nashua, N.H., and interned at VII in Paris, Newsday in New York, and the Harvard University News Office. He holds a B.S. in photojournalism from Boston University.

Pictures:

Abdulai Abubakari holds his infant child, Fakia. (Peter DiCampo/VII Agency)
From his story: Full Frame: Life without lights, by Peter Di Campo, Global Post.

Atlas of the ambient light in the night sky from The night sky in the World.  Large scale image here.

Photo of Peter DiCampo from his website biography.

Links:

Full frame: Life without lights, by Peter DiCampo, Global Post.

More on the effects of light pollution:

A partial bibliography under construction at an Italian website on light pollution.

References

Gislén, Anna, Marie Dacke, Ronald H. H. Kröger, Maths Abrahamsson, Dan-Eric Nilsson, and Eric J. Warrant.  2003. ‘Superior underwater vision in a human population of Sea Gypsies.’ Current Biology 13(10): 833-836. doi:10.1016/S0960-9822(03)00290-2

Korkmaz, Ahmet, Turgut Topal, Dun-Xian Tan and Russel J. Reiter.  2009.  ‘Role of melatonin in metabolic regulation.’ Reviews in Endocrine and Metabolic Disorders 10(4): 261-270. doi 10.1007/s11154-009-9117-5

Navara, K., & Nelson, R. (2007). The dark side of light at night: physiological, epidemiological, and ecological consequences Journal of Pineal Research, 43 (3), 215-224 DOI: 10.1111/j.1600-079X.2007.00473.xPreviousNext 

5 comments

I’ve put in the comments that appeared on the original post.

1. idlemindNovember 8, 2010 at 10:28 pmTerence Dickinson, in his amateur astronomy guidebook “Nightwatch,” relates that after power was severed over a wide area by the Northridge earthquake in 1994 many people called the Griffith Observatory in Los Angeles inquiring about an eerie “silver cloud” they saw after the earthquake. This was, of course, the Milky Way, probably seen by many Angelenos for the first time that morning.I lived less than 2km from the epicenter of that ‘quake, and can confirm that the Milky Way was visible, the first time I’d ever seen it from the L.A. Basin in several decades of living in Southern California.
2. 1. gregdowneyNovember 8, 2010 at 11:17 pmIdlemind —
      Oh, that is bloody brilliant! I hadn’t heard that story, but what a great testimony to the effects of artificial light on our perceptions. I hope you don’t mind if I track that down and use it if I ever write this up for a publication in any way…If you want, send me your name through a direct email (greg. downey at mq. edu. au — take out the spaces and such), and I’ll make sure to credit you with calling my attention to this story!
4. Steve SilbermanNovember 9, 2010 at 12:28 amGorgeous, fascinating post. Thank you!
   
5. jimmypaderNovember 9, 2010 at 4:31 amI first saw the totally dark sky in Montana, the first time I got vertigo.
   I’ve often wondered if increased light levels are related to increased crime rates esp. burglaries.new Arcade Fire titled ‘sprawl II; mountains beyond mountains’:
   “and there’s no end in sight
   I need the darkness
   someone please cut the lights”