Women may be from Mars, but men get more time in the sun…
Looking ahead to International Women’s Day next Sunday, have been wondering why there are so many more women than men living in residential care (a 60/40 split – What is the gender split of people in long-term support?).
And whether that might have anything to do with light.
According to the King’s Fund, women tend to live longer than men, but spend more of that time (20% v 16%) in poor health. We can expect to spend up to 20 years living with some form of disability – but that tipping point happens later for men (61.8 years of age) than women (60.5) – What is happening to life expectancy in England?
As we understand more about the dynamic structural and functional changes in the brain relating to sex and gender identity, some believe it’s time to take another look at traditional ‘binary’ distinctions and define a transgender as a distinct neurobiological phenotype – Neurobiological characteristics associated with gender identity: Findings from neuroimaging studies in the Amsterdam cohort of children and adolescents experiencing gender incongruence.
What’s that got to do with light?
Taking the (imperfect) biological definition, when it comes to preferences for colour temperature and brightness, several experiments suggest that females tend to prefer lower light levels and warmer colour temperatures in a working environment during the day – Effects of illuminance and correlated color temperature on emotional responses and lighting adjustment behaviors. The distinction is maintained in preference and alerting response to evening light, with one study finding increased alertness, improved reaction times and preference for cool light (6500K) for males compared to female participants (2700) – The impact of daytime light exposures on sleep and mood in office workers. Another notes that moderate evening light suppressed melatonin expression more, but failed to deliver the increased alertness for the female participants – the worst of both worlds! – Sex and Seasonal Variations in Melatonin Suppression and Alerting Response to Light.
That increased sensitivity and tendency to choose dimmer settings may be one factor in the increased risk of insomnia and sleep disorders that females experience – up to 58% more according to one literature review – Gender Difference in the Prevalence of Insomnia: A Meta-Analysis of Observational Studies. Female ‘night owls’ are at greater risk of depression than their male counterparts, too – Sex differences in the association between chronotype and risk of depression.
This may be compounded by the fact that women spend less time outside, with this study finding that men spent an average of over 50% more time in bright sunlight than females – Light exposure differs by sex in the US, with females receiving less bright light.
That matters because daytime light exposure, one of the critical predictors of mood, sleep and circadian-related health outcomes – Time spent in outdoor light is associated with mood, sleep, and circadian rhythm-related outcomes: A cross-sectional and longitudinal study in over 400,000 UK Biobank participants.
So perhaps the best way to celebrate International Women’s Day is to take someone you love outside – and then enjoy an early dinner by candlelight.
Pebbles and power law
Have you ever wondered how you can see pebbles and the beach – or the wood and the trees at the same time?
That’s your amazing brain processing the statistical properties of an image and picking out the exception that makes the rule.
Neuroimaging studies suggest that our visual system evolved to respond optimally to the distinctive balance of brightness intensities decreasing across spatial frequency found in natural scenes – i.e. not many very bright or dark areas, mid-number of mid-bright/dark zones etc. When you map that distribution on a graph with a log scale, you get a line or function with a formula known as the 1/fα spectrum, with a gradient of around ~1.25, whether that’s an image of a forest or a beach – Nature in motion: The tuning of the visual system to the spatiotemporal properties of natural scenes.
That seems to be the ‘sweet spot’ between smoothness and complexity that keeps us interested but not overwhelmed. Not only can we see these most easily, we tend to prefer them too – Beauty and the beholder: the role of visual sensitivity in visual preference.
Everyone is slightly different, though and training or priming can radically shift the dial – Visual adaptation to natural scene statistics and visual preference.
If you feel like putting the kettle on and giving your brain cells a run round the block, this article from Quantum magazine is worth a read – A Power Law Keeps the Brain’s Perceptions Balanced.
And if you’re as baffled as I was about what a fourier transform is, this cool article might help – An Interactive Introduction to Fourier Transforms.
Alternatively, get outside and yourself and see the maths in action for yourself.