Blue light makes adolescents more alert

Can school pupils concentrate and perform better if they are surrounded by light of a particular colour? This is the question investigated by a team led by Dr. Petra Studer, neuroscientist, and PD Dr. Oliver Kratz, senior consultant at the Department of Child and Adolescent Mental Health at Universitätsklinikum Erlangen who compared the influence of red-enhanced and blue-enhanced light on attention and quality of sleep in adolescents. Approximately 30 school pupils from grammar schools in Erlangen, aged between 11 and 17, took part in the project led by the Department of Child and Adolescent Mental Health at Universitätsklinikum, Erlangen. On two different days, they came to the ‘light laboratory’, a room with bright lighting, where they were exposed once to blue light, and once to red. After 20 to 60 minutes in this environment, the adolescents completed tests aimed at determining how well they could concentrate. They had to complete arithmetic and reading comprehension tasks, and take a computer-based test to determine their attention levels.

Blue in the morning, red in the evening

The researchers came to the conclusion that, similarly to adults, the attention of school pupils increased in blue light, measured on the basis of their mistakes and the consistency of their reactions – in two out of three attention tests they performed better than when exposed to red light. The colour of the light made no difference to reading comprehension, however. Why do the different colours of light affect the ability to concentrate? ‘Our body clock responds to the different shades, which reflect the natural rhythm of day and night,’ explains Dr. Studer. ‘Blue light is reminiscent of the light in the morning and our brain gets into gear, ready to perform throughout the day ahead. Red light, on the other hand, reminds us of the atmosphere of the evening and signalises that it is time for us to unwind and relax. The first results of the study show that adolescents sleep slightly better after being exposed to red evening light rather than blue light.’

This also explains why some people are more likely to have a poorer quality of sleep if they use their mobile phones before going to bed, due in part to the blue light from the screen. Being exposed to this light in the evening leads to our brains being stimulated at the wrong time of day. Some manufacturers offer a night mode for their devices which emits more red colours, aimed at relaxing the eyes and the brain. Dr. Studer and her colleagues hope that their study will encourage further research into the effects of light on attention and sleep in adolescents. Not only that, but it may also lead to new developments such as lighting designed to provide the perfect conditions for focused learning and healthy sleep.

contact for scientific information:
Further information:
Dr. Petra Studer
Phone: +49 9131 85 39123

original publication:
The results have been published in the journal ‘Physiology & Behavior’ (vol. 199, pp 11–19).
The study can be found (in German) at:

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