Posts Tagged ‘circadian rhythm’

I was intrigued by this photo of an intensely interested Zoe taken when she was seven months…Watching a tree The scene Zoe was watching

…because this is what she was looking at – not just once and briefly, but repeatedly for minutes at a time.

It may have been the leaves that captured and held her attention but I think that it was more likely the blue sky.

A couple of months before, I was watching her as she was being pushed along in her pram. The hood was down as the sun was low in the sky. She was lying on her back but it was obvious that something was attracting her attention. She kept tilting her head backwards clearly intent on taking in the view overhead. All there was to see, as far as I could tell, was the sky, which on that day was an expanse of blue. Those with me, including her mother, agreed. We realised that this might well have been Zoe’s first experience of the wide blue sky.

Zoe’s response is not surprising. The colour blue, especially sky blue, has a distinctive and spontaneous effect on all of us. It works on our brains to stimulate feelings of calmness, relaxation and well-being. Little wonder that sky blue is a universally popular colour, which enhances enormously the appeal of real, painted and photographed landscapes. It also plays and important part in heightening the attractiveness of water views.

Landscape painting b Zhang's study 3 more beautiful

Strictly speaking it is not the “blueness” of blue that produces its emotional effect. Blueness is the product of brain activity stimulated by short-length light waves falling on special colour cells (cone cells) in the retina at the back of our eyes. Because our brains can differ in the way they process the information from cone cells, it is possible that the “blue” you see is not the same “blue” I see. This is true for all visible colours. But even if my blue is your red, both of us will still say that the sky is blue and a strawberry is red.

Where blue is concerned, however, the picture is a little more complicated. Scientists have discovered that there is a second colour-sensitive pathway linking our eyes and brain. This pathway begins with cells in the retina that contain melanopsin. This is a pigment that is sensitive to blue light. Its presence enables our eyes to gauge both the amount of blue and yellow in incoming light and the intensity of that light. The pathway carries this information directly to parts of the brain involved in emotion. So the emotional effect of blueness is the same for all of us regardless of any differences in the blue that we are actually seeing.

The information is also transmitted to those parts of the brain responsible for the regulation of the circadian rhythm – the daily cycle of waking and sleeping. Bright blue light signals daytime and prompts wakefulness while its absence triggers the production of the sleep hormone melatonin. (Yellow-red firelight on the other hand makes us drowsy.)

Another interesting thing about blue light is that it improves memory and the expansive kind of thinking involved in creativity. For example, researchers gave over 600 participants six different cognitive tests presented on computer monitors that had blue, white or red backgrounds. If the task was creative, like brainstorming or drawing a picture out of a bloodstain, participants did twice as well with blue backgrounds as they did when the background on the monitor was red.

Why blue encourages us to be broader and more flexible in our thinking is not understood. Perhaps it is because we associate blue with the vastness of the sky and the ocean, and this somehow enables us to broaden our mental horizons.

I would like to think that Zoe was beginning to discover the vastness as well as the blueness of the sky.


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Talking recently to her junior primary school class, my friend, Rosemary Clarke, used the word, “picnic”. “What’s a picnic?”, the children asked. Unlike the happy toddler and her baby sister in this photo, these children from a Sydney suburb had never eaten a meal under a tree in a park or on the bank of a river or even on one of Sydney many beaches.

Family picnic

The photo, it should be said, was taken over 25 years ago when the world of childhood was different but beginning to change. In the past two decades, children’s recreational contact with the natural world has declined dramatically as indoor activities have substantially replaced outdoor play. In 1981, according to surveys conducted by the Institute for Social Research at the University of Michigan, children ages 6 to 17 spent an average of 100 minutes outdoors in unstructured play each week. By 2002, that time was halved to a mere 50 minutes.

In one generation, the proportion of children regularly playing in wild places in the UK has fallen from more than half to fewer than one in 10. In the US, in just six years (1997-2003) children with particular outdoor hobbies fell by half. Eleven- to 15-year-olds in Britain now spend, on average, half their waking day in front of a screen.

The story in Australia is much the same. For example, a recent Western Australian study found that over 70% of primary children reported participating in more than the recommended maximum of two hours electronic media activity on all of the seven days prior to the survey. Similar proportions of children exceeding guidelines have been revealed in other Australian and international research.

Does it matter that indoor activities are displacing outdoor play? Will children’s development, health, happiness and well-being suffer as a consequence?

Yes, is the answer commonly given by professionals involved with children and their welfare. Richard Louv, for example, claims that impoverished contact with the natural world places children at risk of what he calls nature-deficit disorder. This is not a medical diagnosis but a label for the costs to children of being disconnected from nature. The costs Louv describes include inadequate and inappropriate sensory stimulation, attention difficulties and higher rates of physical and emotional illness.

Louv’s concern is shared by many othersand is based largely on observations of the benefits children obtain from living, learning or playing in natural environments. These benefits include

  • improved physical fitness and co-ordination,
  • lower likelihood of obesity,
  • less risk of short-sightedness (myopia),
  • less stress,
  • increased self-esteem,
  • strengthened self-control,
  • enhanced academic motivation and performance and
  • relief from some of the symptoms of Attention Deficit-Hyperactivity Disorder.

It is also widely believed that, by promoting free, unstructured and creative play of the kind these kids are having, nature provides optimal stimulation for healthy brain development. IMG_0600

What being nature-deprived means for children’s long-term development and functioning as adults has still to be discovered. But there are immediate consequences we already know about, for example:

  • they have less exposure to the sky-blue light that, in children especially, has a potent influence on human sleep patterns, hormonal and chemical rhythms, mood and alertness;
  • they have less of the colour, depth and motion stimulation needed for the development of full visual powers;
  • their awareness and understanding of the natural world is impaired. The decline in children’s basic knowledge of nature is now being documented. A United Kingdom survey commissioned by the Airbus Corporation found, for example, that 37 per cent of children aged between 5 and 10 did not know what a bee looked like and a third could not recognise a mouse;
  • they are at risk of becoming fearful of nature and even contemptuous of whatever is not “man-made, managed or air-conditioned”.

In having much less free play in natural settings, the children of today are missing out on what I call an authentic childhood.

I’ll have more to say about this in posts to come.

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When I am camping I sleep well. I feel sleepy earlier than I normally do and I wake earlier and brighter than is usual for me. An obvious explanation is that the exertion of backpacking and setting up camp makes me tired and ready for a good night’s sleep. But there is another reason.

You can see in this photo of a campfire that the light falling on the eyes of the eyes of the campers is at the red-orange end of the spectrum.

ab The first campfire

That light triggers cells in the back of their eyes to tell their brains it is time to increase the output of a hormone called melatonin. Increased melatonin causes us to feel sleepy. Bright morning light on the other hand decreases melatonin levels and enables us to wake from sleep feeling bright and alert. This cycling between lower melatonin levels – wakefulness – and higher levels – sleepiness – is called the circadian rhythm.

The circadian rhythm is critically important to our health not only because its effects on sleeping but also because it affects the immune system, appetite and hunger regulation, temperature and blood pressure and mental efficiency.

The key to having a healthy circadian normal rhythm is exposure to changing natural light. Our brains are adapted to the intensity and daily variations of natural light. During the day, natural light is brighter and “bluer” for the first half but becomes less bright and “redder” as sunset approaches. When we are exposed to these natural light conditions our circadian rhythm and the daily light-dark cycle fall into line. We awake refreshed and alert soon after sunrise and find ourselves looking forward to sleep once the sun has set.

In our modern lifestyle, the match between natural light conditions and our circadian rhythm is often disrupted. Many of us work all day in artificial light. Almost all of us experience light well beyond sunset. Using Ipads and other appliances with back-lit screens at night is especially disruptive as these deliver blue rather than red spectrum light.

One major effect of artificial lighting is to create a lag between the natural light-dark cycle and our circadian rhythm. A recent study has demonstrated, however, that this lag disappears within a week if people experience only natural light and then only the light from a campfire at night.

Other ways of claiming the benefits of natural lighting include:

  •  taking a short walk in the early morning sunlight
  •  using your  “sunnies” sparingly in the morning
  •  having a “sunshine break” during the day (particularly important if you spend the day in artificial lighting and also for maintaining your production of vitamin D)
  •  softening domestic lighting in the hour before bedtime
  •  avoiding using back-lit appliances leading up to bedtime

I doubt that Seneca the famous Roman philosopher and statesman would have imagined this application of his suggestion that “We should all live according to nature”.

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