The research, published in Scientific Reports, compared how the pupils of younger and older people reacted to different aspects of colour in the environment.

The team recruited 17 healthy young adults with an average age of 27.7, and 20 healthy older adults with an average age of 64.4.

Participants were placed in a blackout room and shown 26 different colours for five seconds each, while the researchers measured the diameter of their pupils.

Pupils constrict in response to increases in colour lightness and chroma (colourfulness).

The colours shown included dark, muted, saturated and light shades of magenta, blue, green, yellow and red, alongside two shades of orange and four greyscale colours.

Using a highly sensitive eye tracking camera*, which recorded the pupil diameter at 1000 times per second, the team found that the pupils of healthy older people constricted less in response to colour chroma compared with young adults. This was particularly marked for green and magenta hues.

However, both younger and older adults had similar responses to the ‘lightness’ of a colour shade.

The study is the first to use pupillometry to show that as we grow older, our brains become less sensitive to the intensity of colours in the world around us.

The findings of the study also complement previous behavioural research that showed that older adults perceive surface colours to be less colourful than young adults.

Lead author, Dr Janneke van Leeuwen (UCL Queen Square Institute of Neurology), said: “This work brings into question the long-held belief among scientists that colour perception remains relatively constant across the lifespan, and suggests instead that colours slowly fade as we age. Our findings might also help explain why our colour preferences may alter as we age – and why at least some older people may prefer to dress in bold colours.”

The researchers believe that as we get older there is a decline in the body’s sensitivity to the saturation levels of colours within the primary visual cortex – the part of the brain that receives, integrates, and processes visual information relayed from the retinas.

Previous research also showed this to be a feature of a rare form of dementia called posterior cortical atrophy (PCA), where noticeable difficulties and abnormalities in colour perception could be due to a significant decline in the brain’s sensitivity to certain colour tones (specifically green and magenta) in the primary visual cortex and it’s connected networks.

Co-corresponding author, Professor Jason Warren (UCL Queen Square Institute of Neurology), said: “Our findings could have wide implications for how we adapt fashion, décor and other colour ‘spaces’ for older people, and potentially even for our understanding of diseases of the ageing brain, such as dementia. People with dementia can show changes in colour preferences and other symptoms relating to the visual brain – to interpret these correctly, we first need to gauge the effects of healthy ageing on colour perception. Further research is therefore needed to delineate the functional neuroanatomy of our findings, as higher cortical areas might also be involved.”

This work was undertaken as part of an interdisciplinary residency with the Created Out of Mind consortium, recipients of the Wellcome Hub Award 2016-2018.

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