Light bulbs vary not just technically but also produce different kinds of light. LEDs stand out in comparison to halogen and incandescent bulbs through the high proportion of blue and low proportion of red light. This difference does not fundamentally change in LEDs even with warm light. The effects of the high-energy shortwave blue light in LEDs are increasingly being debated in connection with the frequent use of monitors and smartphones. They have been medically shown to produce sleep disorders and retinal damage.

Higher failure rate with LED light

When a school replaces its lighting, energy and cost savings as well as sufficient brightness are important aspects. Another aspect is how the children cope with the new lighting. I asked myself this question together with some others one-and-a-half years ago. This led to a series of studies with pupils in a class 5.

In all the studies, the colour temperature (between 2700 und 3000 K) and light intensity were as similar as possible. The features to be tested were agreed with the class teachers.

The first question was whether the children would react at all to the different types of light. We tested that with a number of tasks. On two days each week over a period of two weeks comparable tasks were set in the sequence LED/halogen and halogen/LED which consisted of retelling a story, a dictation and copying a text.

To our great surprise there were large differences. In the four pieces of work testing spelling, the mistakes under LEDs lay at 116, 160, 310 and 313 percent in comparison to halogen. When copying a text under LEDs, verbs were more frequently transposed and in retelling a story the correct person was less frequently used.

These results called for a repeat. Studies were carried out at another Waldorf school in early 2017 in a class 3, 5 and 7. Here the comparison was between LEDs and the incandescent bulbs previously in use. Our aim was to test possible effects on memory, mental imagery, imagination and empathy in various tasks.

In the class 3, the error rate when copying from the blackboard under LEDs was higher (140 percent) whereas it was a little lower for mental arithmetic and dictation (87 percent and 88 percent). On two occasions the class painted pictures, once in free-form and once on the subject of animals. The two sets of pictures were anonymised and then evaluated by an experienced Waldorf teacher. The pictures painted under LEDs were significantly smaller, less coloured in with less pronounced forms. The differences were even greater in the animal pictures.

In the class 5 only the dictation and copying from the blackboard could be evaluated. In both cases more mistakes were made under LEDs (114 percent, 173 percent).

This was confirmed in the class 7: in dictation and mental arithmetic there were more errors under LEDs (215 percent, 109 percent). In the free telling of a story, the texts written under LEDs were significantly shorter (58 percent). We asked a graphologist to make a detailed assessment of the handwriting in the anonymised dictations. In summary, the handwriting under incandescent bulbs tended to be more spontaneous and age-appropriate and that under LEDs was characterised as under stress.

Stronger pictures under halogen light

More recently, we had the opportunity to have children in a kindergarten and a class 2 of a special needs school paint pictures under halogen and LEDs. In the kindergarten, we asked the children on three occasions to paint a picture as usual, first under halogen, then under LEDs, and finally under halogen again. These sets of pictures from the thirteen children were anonymised and then assessed by a Dutch teacher. On the first and third occasion a greater number of children also filled the reverse side of the pictures with painting, namely six and four times in comparison to twice on the second occasions (LEDs). The pictures under halogen were also more frequently full and powerful, namely six and five times in comparison to just twice on the LED occasion.

The observations of the teachers are also interesting. They point to new avenues of investigation. The teacher in the special needs school, for example, noted a behavioural change in her most sensitive pupil, an autistic boy: on both occasions under LED light the pupil became tense and ripped up his picture whereas otherwise the participated in painting peacefully and with little involvement.

We are only at the beginning with our work on the possible effects of using LED lighting in schools. We are therefore interest in additional schools who are prepared to throw more light on knowledge about this subject through studies. Even if our work so far is in the nature of preliminary studies, their relatively high conformity produces a certain picture. How does this picture fit in with current findings in the scientific literature?

Improvement of concentration with LEDs

In an LED study funded by the German education ministry, 33 schools were followed as they converted to LEDs. After the changeover, the pupils were asked about the lighting situation which they graded as being one school mark better than previously. The previous lighting had consisted primarily of fluorescent tubes, some of which were defective or dirty. In some schools, windows, floors, heating and ventilation were also replaced. It cannot therefore be judged to what extent the result was due to the renovation or the lighting.

Oliver Keis and his colleagues at Ulm University wanted to confirm with their study that LED lighting with a high proportion of blue light leads to an improvement in alertness and cognitive performance under practical school conditions. In the largely male pupils aged approximately 19, the speed of cognitive processing and concentration did indeed improve under white LEDs (5500 K). Memory performance did not improve.

Asked for their opinion about the lighting, the pupils preferred the previous lighting with fluorescent tubes. The tests were undertaken in the early hours of the morning. Significantly the authors noted that they had avoided using blue-enriched lighting in the evening or at night to prevent sleep disorders.

Increased reading speed and stress

In Hamburg, a study in cooperation with a lighting manufacturer some years ago tested whether the performance of pupils could be increased through brighter LEDs with a high proportion of blue light. The reading speed did indeed increase with a high proportion of blue light. At the same time the children fidgeted more in the lesson and the level of the stress hormone cortisol rose. The lighting was regulated by the teachers. Although the teachers wanted to continue to obtain the greatest concentration in the children by using the lighting, the study was abandoned because parents kept complaining about their hyper children.

What is the goal?

If we look at the current studies and our own initial results, there are not many differences and some similarities. LEDs are mostly compared with fluorescent tubes. Incandescent bulbs or halogen lamps which we included in our tests by comparison possess a much more balanced spectrum. The studies mostly looked at cognitive performance such as reading speed or concentration. The only results in our studies which showed a slight advantage of LEDs were in dictation and mental arithmetic in the class 3. With regard to memory performance there was no improvement in the Ulm study as a result of LEDs. Copying a text or from the blackboard calls on the memory. In our own studies the differences here were particularly pronounced. Imagination is required when painting a picture or freely telling a story.

Here too there were large difference in our own studies. Unfortunately the corresponding comparisons are absent in the major studies.

Which artificial light is good for our children? The answer would appear to depend on our goals: cognitive performance, memory, the ability to paint, imagination or empathy, or perhaps the whole human being? For the sake of our children we should look more closely at the subject of artificial light.

About the author: Dr. Uwe Geier is chief executive of Forschungsring e.V. and WirkSensorik GmbH. The focus of his work is food quality. He has developed the EmpathicFoodTest to measure food-induced emotions.