Red – the ‘marmite’ colour?
You’d have to have been living in a cave last week to have missed the annual rampage of red hearts/roses/chocolates/cards for valentine’s day.
But when it comes to decor, as I discovered during a lively conversation at Camira last week, red isn’t everyone’s cup of tea. So what’s going on?
Reflection v emission
It’s worth differentiating between things that ‘look red’, meaning, counter-intuitively, that they reflect all the wavelengths except red; and light sources that ‘look red’, which means they generate photons with a dominant wavelength between around 620 to 750nm. (not to be confused with infra-red extends beyond the visible spectrum, defined by the CIE as a range from around 780nm to 1mm – Infrared radiation.
From sensing to seeing
When it comes to how your brain translates those photons into perception, a subset of cones in your retina responds thanks to a light-sensitive protein or ‘opsin’ (the not very imaginatively-named ‘lw opsin‘) – Cone Opsin. The ability to perceive colours develops during the first year of life: by six months, a baby can discriminate between basic colours and maintain some constancy or stability even when the lighting changes – the banana is yellow whether it’s outside or in the kitchen – Infant color perception: Insight into perceptual development. That ‘wiring and firing’ process seems to respond to the range of tones in the natural environment, leading some to argue that the current trend for neutral colours, or ‘mushroom motherhood’ may be storing up problems for later life – COLOR AND COGNITION: EVALUATING THE EFFECTS OF MONOCHROMATIC ENVIRONMENTS ON CHILDREN’S PSYCHOLOGICAL AND CREATIVE GROWTH.
At the other end of the age scale, we tend to lose our ability to see colours clearly, especially in the red, or longer wavelength part of the spectrum – Age-related changes of color visual acuity in normal eyes.
Until relatively recently, scientists thought that we ‘see’ colours along three critical axes – blue-yellow, red-green, and black-white ‘lightness’, and that the primary and secondary colours that arise from that model were stable and shared across cultures (Hering’s ‘colour-opponency’ theory) – The colour hexagon: a chromaticity diagram based on photoreceptor excitations as a generalized representation of colour opponency. But new evidence has challenged that paradigm, demonstrating that our experience of colour is highly context-driven – Color appearance and the end of Hering’s Opponent-Colors Theory.
While the personality-preference link does not seem to be backed by research, brain imaging studies do suggest that red increases saliency or attention, especially in emotionally-charged settings – The Early Facilitative and Late Contextual Specific Effect of the Color Red on Attentional Processing [Original Research]. For example, we may find it easier to spot an angry face against a red background, but not a neutral or happy one – Active Language Modulates Color Perception in Bilinguals, while another study found an increase in aggressive behaviour in a classroom with red walls compared to white – The Effect of Classroom Red Walls on the Students’ Aggression. Another found that students found it easier to focus in classrooms with a blue- to questions presented in red typography tended to make more hasty decisions than those presented in blue. But the methodologies are patchy, and the sample sizes are small – and there is no mention of the quality of the light – The Association between Physical Environment and Externalising Problems in Typically Developing and Neurodiverse Children and Young People: A Narrative Review…
A rose by any other name?
Whether you love red or not, the number of words you have to describe that part of the colour wheel will shape the way your brain processes objects of that particular hue: not only will you will find it easier to hold them in your working memory – Richer color vocabulary is associated with better color memory but not color perception – Richer color vocabulary is associated with better color memory but not color perception, but some suggest that colours may coded as concepts in the brain – Perception of color in primates: A conceptual color neurons hypothesis, in a similar way to ‘place’ and ‘number’ neurons – Hippocampal neurons construct a map of an abstract value space.
In a (colour) world of your own?
Around one in 12 men has a colour vision difference. The most common form involves difficulties in distinguishing red from green because of dysfunction or absence of those cells. While new photosynaptic devices may one day effectively ‘fill in’ the signals and ‘restore’ full colour vision, being a dichromat may be a secret superpower. This team used eye tracking to understand the difference in attention or gaze between those with ‘normal’ trichromatic vision and dichromats. Interestingly, they found that those with dichromacy tended to have a more idiosyncratic approach to exploring the scene – Influence of colour vision on attention to, and impression of, complex aesthetic images.
So what’s your favourite colour?
When it comes to choosing colours for a home, office, healthcare setting or a school, the level of contrast, saturation and lightness, context and personal preference – and the quality of natural and artificial light, of course, may turn out to be more important than the hue itself – The Language of Color in Home-Office Design: Emotional, Perceptual, and Functional Dimensions of Wall Colors.
Green light for pain relief
Maybe you’re one of the estimated one-in-seven people who suffer from migraine headaches, a complex neurological disorder that can lead to crippling throbbing pain, often on one side of the head – About migraine.
Migraine may even be a risk factor for dementia, with one study finding that people with migraines were at 50% higher risk of developing the disease – Migraine is a risk factor for dementia: a systematic review and meta-analysis of cohort studies.
Researchers have known for over 15 years that narrow-band green light – at 520 ± 10 nm, selectively activates medium wavelength cones and reduces the severity and frequency of migraine.Their ground-breaking work led to the discovery of a new pathway that links the brain areas involved in vision to the circuits that mediate the distinctive pain profile of migraine, as well as sensory processing, attention and memory – A neural mechanism for exacerbation of headache by light.
There’s growing evidence of a dynamic link between narrow-band light exposure and a cascade of responses, including opioid signalling and inflammation, that may have implications for pain management in fibromyalgia and post-surgical recover,y too – Green Light Exposure Improves Pain and Quality of Life in Fibromyalgia Patients: A Preliminary One-Way Crossover Clinical Trial, Green Light Antinociceptive and Reversal of Thermal and Mechanical Hypersensitivity Effects Rely on Endogenous Opioid System Stimulation.
The insights from the lab are now being translated into the real world, with one peer-reviewed study using an ‘off the shelf’ product to show that two hours of daily green light exposure can effectively reduce the frequency and severity of migraines with a ripple effect on photosensitivity, anxiety and sleep – Narrow band green light effects on headache, photophobia, sleep, and anxiety among migraine patients: an open-label study conducted online using daily headache diary [Original Research].
Even if you aren’t struggling with migraine, a gentle stroll in the woods or the park could deliver your daily anti-inflammatory, stress-relieving dose of green wavelengths – and mitochondria-boosting infra-red without costing the earth – Exploring the Optical Properties of Leaf Photosynthetic and Photo-Protective Pigments In Vivo Based on the Separation of Spectral Overlapping, Artificial-Light Culture in Protected Ground Plant Growing: Photosynthesis, Photomorphogenesis, and Prospects of LED Application.
Puddles and photons
It’s been raining non-stop over here in the UK, so there’s been ample opportunity to marvel at the beautiful patterns created by run-off from gutters and fields. I was consigned to the bottom stream in Physics class at school, but these dynamic peaks and troughs remind me of one of the only hands-on experiments that I actually understood. We sent a vibration through a tank of water and watched the waves ‘add up’ (constructive interference) or cancel each other out (destructive interference).
You can do that with a stream of photons.
When you shine a light with the same wavelength as the gap between atoms through a crystal, the pattern of bright and dark spots – the constructive and destructive interference – gives you detailed information about the structure of the crystal itself. That technique, called x-ray crystallography, pioneered by Lawrence Bragg at the turn of the 20th century, was used by Rosalind Franklin in her celebrated Photo 51, which held the key to discovering the structure of DNA. A new opera about her work is coming up at King’s College, London – links to tickets here if anyone is free to join.
It’s also the foundation for the next generation of ‘resonant cavity’ LED’s. These chips are engineered within fractions of a nanometer to bounce the photons around inside a cavity to stack up those wave forms before releasing them through a series of microlense arrays and reflectors, delivering more stable more efficient and more vivid displays – Optimization of dispersion angle in resonant cavity micro-light-emitting diode using multilayer DBR and microlens structures.
More everyday magic –