‘Lighting’ is a theme in the chapter ‘installations and appliances’. (See The recommendations.) This theme has much in common with ‘light and sight’. There the message is that daylight is nearly always to be preferred over artificial light, which is the subject here. Artificial light is unavoidable after sundown and in places where daylight is obstructed.
Generally, artificial lighting influences the emotions and mood, the atmosphere, esthetics and the spatial experience. Just as daylight, but probably to a lesser extent, abundant lighting is thought to increase achievements in school and the work place, probably because of an unconscious influence on motivation.
Moreover, and still in general, light effects are also caused by non-visual mechanisms, which is to say the influence on day- and night-rhythm and the biological clock (the circadian rhythm). ‘Non-visual’ because stimuli which enter the eye through retinal ganglion cells don’t reach the visual cortex. Through hormonal cues light arouses a state of alertness in many different brain areas.
Light gains in importance in the case of autism because so many abnormalities occur in its perception. In ‘light and sight’ some prevalent problems of vision were briefly mentioned, among which short- and far-sightedness, strabismus and lack of contrast-perception. Since we see the world around us through light entering the eye, such abnormalities are relevant in this context. Of special interest is the fact that over-sensitivity to light is quite prevalent among people on the spectrum.
The broad relevance of suitable lighting
Lighting is relevant in the three broad design issues which are distinguished on this site: orientation, interaction/communication and the sensory. (See ‘autism characteristics’.)
To achieve a clear visual structure, the spaces in a home or building should be sufficiently illuminated in order to meet the limitations of many autistic people which stand in the way of their overview. Such overview is enhanced by soft and even lighting while strong lighting causes annoying drop shadows and dark patches which people on the spectrum often have difficulty interpreting correctly. What’s at stake here – as elsewhere because of coherence problems – is that changing a single element in a situation may lead to experiencing a whole new situation. Also the principle of ‘zoning’, by which well-defined (parts of) spaces have the lowest number of functions, can be achieved, for instance by creating withdrawal spaces with their own task lighting.
Because autistic children and adolescents often are extra afraid of the dark well lit staircases and hallways are advisable, as are bedside or night lamps. There too drop shadows can be confusing or frightening.
Good illumination can also serve the purpose of lessening interaction and communication difficulties. Mostafa says that stairwells and corridors should be well illuminated while avoiding glare and silhouetting. The latter not only because of visual handicaps but also for those with hearing problems which they compensate by looking for social cues in body posture and facial expression. These are not the only uses of lighting in the social domain. So, for instance, lighting may have the same function as sightlines: improving opportunities for observation and the prevention of bullying.
Visual processing difficulties in the brain impact directly on the light design and the choice of certain types of lamps. Usually these hinge on hypersensitivity to light, although hyposensitivity also occurs.
Special attention is needed to avoid reflection and glare. For this one can choose the right reflective surfaces, apply diffuse lighting and/or avoid or minimize high placed light sources.
Fluorescent lighting, adaptations and incandescent lighting
The most common recommendation regarding artificial light is to avoid fluorescent lighting. Many on the spectrum experience strong negative effects of its flicker. In one study five autistic children were compared to five intellectually impaired children under conditions of fluorescent and incandescent lighting. It appeared that half of the autistic children in the fluorescent lighting condition exhibited significantly more stereotypical behavior. There are even indications that a flicker frequency of up to 60 Hertz can be perceived by people on the spectrum. In addition there is the irritating humming to which many on the spectrum are quite averse. (By the way, fluorescent lighting apparently has considerable health risks for everybody. See Codinhoto et al.)
The story doesn’t end here, however. According to Christopher Henry there is an apparent consensus with regard to fluorescent lighting, however “reaching an agreement against poorly designed fluorescent lighting is one thing, resolving how to light an autism facility is another.” Indeed we see many experts, among whom Humphreys, who apply compact fluorescent lighting or CFL’s instead. Beaver: “Compact fluorescent is acceptable but the specification always needs to be checked to make sure that fittings are fitted with the appropriate diffusers.” Others (such as Brand) advise to “Fit non-flickering lighting such as electronic ballast fluorescent lamps, which flicker at an imperceptible frequency and are less likely to aggravate light-sensitive residents.”
However, in what seems to be a very well researched article, the psychiatrist Victoria Dunckley argues against CFL’s. Their flicker may be imperceptible, this doesn’t rule out an adverse effect. She mentions severe stress and an adverse effect on the biological clock. These conclusions are drawn for the general but ‘sensitive’ population and seems to hold even more for those on the spectrum.
Somewhat contradictory to the above seems an appeal of the National Autistic Society (NAS) to the British government to continue to make incandescent lighting available to those who need it because of medical reasons, among whom are people with autism. In September 2012 the EU banned the sale of such lamps and nothing came of this appeal. Notwithstanding an Internet call which yielded (non-representative) responses from 43 people on het spectrum of whom 41 said to experience strongly negative effects from the new types of lighting. Thirty-five said to stockpile incandescent lamps. The NAS experts take these responses very seriously.
All in all it seems clear that fluorescent lighting should be avoided, including CFL’s. By and large the literature on light and autism hasn’t kept up with the pace of technological development, there is not much on LED-lighting and less on halogen lamps. According to some on the spectrum both are much preferred. At least one school has been entirely fitted with LED lighting. Reports on LED’s efficacy of more than three years ago still raise doubts, but it seems that there has been so much progress in recent years that LED-lighting is now one of the preferred light sources for many people on the spectrum. Meanwhile we tend to agree with Victoria Dunckley that the generally preferred order is: sunlight or candle light, followed by incandescent, then halogen (although, as remarked, there isn’t not much on this), then LEDs, then CFL’s. As usual, allowances have to be made for individual differences.
Other indoor lighting measures
Other lighting measures can be taken which don’t particularly concern sensory issues. Safety is an obvious concern since both visibility (stairwells, emergency lighting) and the dangers associated with electricity come into play.
Familiarity & Clarity is one of Ahrentzen & Steele’s design goals which has much to do with ease of operation of electric appliances among which lamps.
Although most measures are directed at oversensitivity for light, some take people who are under-sensitive into account as well.
Especially in the case of treatment, and long-stay homes, adequate lighting of outside areas and entrances is mandatory. Around homes for (semi-) independent living outside lighting around doors and yards are recommended as well. This may be triggered by timers or light sensors. Motion sensors are dissuaded because of their startling or frightening effects.