Colours on the brain – and the sweet taste of pink

Rainbows under the radar

Most of us take colour for granted.

That’s a pity because your experience of a technicolour world is a piece of everyday magic, evolved over 65 million years ago and still holds the key to mental and physical health worth fighting for –Ancestral photoreceptor diversity as the basis of visual behaviour.

Your brain ‘sees’ a colour as a response to a bundle of wavelengths, given off by a light source, bouncing off an object and filtered through your eye.

So your brain can only ‘see’ wavelengths that were given off by the light source to start with.

Making sure the lights offer a full and balanced spectrum to start with is even more critical for the one in 12 men and one in 200 women who experience Colour Vision Deficiency – where their ability to distinguish between colours, most commonly red and green – is impaired – The Genetic and Evolutionary Drives behind Primate Color Vision.

The problem…

Energy performance ratings are based on the brightness, or lumens, per watt or unit of energy. If you want to optimise efficiency, you don’t ‘waste’ energy generating wavelengths that don’t contribute to the energy performance score on the box.  So most LEDs are engineered to deliver a highly compressed set of visible wavelengths compared to daylight – the ‘real thing’.

It’s like the difference between a live concert and an Mpeg file. A digital file gives the general idea, but lacks the subtle dynamics of the real thing.  And just as there are sound frequencies we can’t hear, there are wavelengths of light we can’t see, but we can still sense the difference.

Recent research that compared conventional LED sources with those with a spectral distribution closer to daylight found improved working memory, processing speed, procedural learning, and testing accuracy  with young adults under daylight-like light spectrum lighting

compared to conventional-LED spectrum lighting…” – Effect of daylight LED on visual comfort, melatonin, mood, waking performance and sleep. Another found a significant decrease in stress levels with an increase in colour rendering index from Ra=” 80-85″ to Ra = 96). “ – Effects of CRI and GAI on Emotion and Fatigue in Office Lighting.

So how can you tell what’s coming out of a lightbulb when you can’t consciously ‘see’ it?

The basic industry measure is the Colour Rendering Index (CRI)

The Color Rendering Index (CRI) was the first metric developed to characterize how colors appear under various light sources. CRI is based on a scale from 0 to 100, with 100 indicating that colors under the light source appear the same as they would under natural light. However, CRI has its limitations. It only represents color fidelity—accuracy—not the more subjective quality of perception—how well it looks to the human eye. Moreover, it’s based on only eight pastel colors, which is not representative of the full color spectrum.

TM30

The ANSI/IES TM-30 Standards are an internationally accepted set of guidelines for characterizing the color rendition performance of virtually any light source – TM-30 is more comprehensive and consists of three parts: a Fidelity Index, Gamut Index, and the Color Vector Graphic. These combine to give a more accurate picture of a light source’s color faithfulness and better accounts for the outstanding color rendering abilities of LEDs. TM-30 was developed to encompass more aspects of light appearance, and to provide a more accurate measure of newer light sources such as LEDs.

CRI vs TM30

While CRI is a familiar and long-standing color rendering metric, lighting experts have long noted its limitations. With today’s high-quality LEDs, a difference of just 4-5 points in the CRI (e.g., 80 CRI vs 85) is very noticeable. LEDs can produce light that produces a poor CRI score, but that looks good to humans. On the other hand, TM-30 provides a more detailed and accurate measure of color rendering, making it especially relevant when average color fidelity is an important consideration – Ancestral photoreceptor diversity as the basis of visual behaviour.

So what can you do?

• Make the most of daylight and windows
• Balance the quality-efficiency trade-off by using lights with a high colour rendering index and good TM30 scores in spaces where accuracy matters and particularly for children who are learning about the world
• Be aware of how colleagues and family members see colour and make adjustments for those who see the world through a different lense.

Pink Facts for your valentine

1. A sweet pink drink improves strength endurance performance compared to the same drink without colouring (or no drink at all) – (average number of bench presses up from 56 to 60).  Surprisingly, the athletes in both conditions felt they were putting in the same effort – The placebo effect of a pink non-caloric, artificially sweetened solution on strength endurance performance and psychological responses in trained individuals.
2. Carbohydrate mouth-rinse before running can improve performance by up to 3%. A non-calorific solution could have a similar effect – if you add some pink colouring. This study found participants improved speed and distance on a running machine by over 4%, and even enjoyed the run more – Mouth Rinsing With a Pink Non-caloric, Artificially-Sweetened Solution Improves Self-Paced Running Performance and Feelings of Pleasure in Habitually Active Individuals.
3. Rose-tinted glasses  research suggested that seeing through red lenses increased activity linked to arousal compared to no lenses. They also found increased arousal with green lenses, but only for pleasant images – Tinted lenses affect our physiological responses to affective pictures.

What’s going on?

This fascinating paper points to the universal connection between the colour pink and sweetness – On tasty colours and colourful tastes? Assessing, explaining, and utilizing crossmodal correspondences between colours and basic tastes. Sweet foods in nature deliver a high sugar content. We evolved to seek out high-calorie foods and learn to choose pink foods over other colours in the first weeks of life – Infants’ sensitivity to arbitrary pairings of color and taste. As a result, we expect foods which are pink to be sweet. This in turn increases our response.

Learning to read with colour

Dyslexic children see the world differently and often struggle to read.

They tend to have a different number and longer fixations (the time the eye stays on a fixed point on a page or screen.)

There have been mixed results for coloured overlays, pioneered by clinicians linked to Meares Irlen Syndrome.

But this study, using EEG and eye tracking was able to identify some of the mechanisms involved. It noted that that the turquoise background, turquoise overlay, and yellow background colours were particularly valuavble.

Reducing the time reading tasks took and shifting the brain wave signature: children have higher values of beta (15-40 Hz) and the broadband EEG (0.5-40 Hz) power while reading in one particular colour (purple), as well as increasing theta range power while reading with the purple overlay – The Relation between Physiological Parameters and Colour Modifications in Text Background and Overlay during Reading in Children with and without Dyslexia, The Role of Visual Factors in Dyslexia.