A considerable body of research shows that people prefer daylit spaces to those lacking natural light. Why should this be? If there is sufficient light to see, why would people prefer one source to another? To answer this question, we need to understand the evolved relationship between humans and natural light.
By Judith Heerwagen, Ph.D., environmental psychologist in Seattle, Washington.
Daylight from an evolutionary perspective
Prior to the advent of buildings, humans lived immersed in nature. Daily activities were aided or constrained by the presence or absence of daylight and by qualities of light that signalled time and weather. Our physiological systems – especially our sleep-wake cycles – were in synch with the diurnal rhythms of daylight, as were our emotional responses to light and darkness. The strong, consistent preference for daylight in our built-up environments today suggests that evolutionary pressures are likely to be influencing our responses.
There is an innate need in human beings to be in touch with nature. The acceptance of buildings is therefore crucially dependent on the extent to which they enable contact with external surroundings.
Although all our sensory systems acting together were important to survival, the visual system is our primary mode of gathering information. Thus, light must have played a powerful role in information processing and survival. In ancestral habitats, light was likely to have had several key functions that are relevant to the design and operation of built-up environments. These include:
- Indicator of time. Natural light changes significantly over the course of the day, providing a signal of time that has been crucial to survival throughout human history. Being in a safe place when the sun was setting was not a trivial matter for our ancestors, and it is still important to human well-being.
- Indicator of weather. Light also changes with weather, from the dark, ominous colour of storms to rainbows and beams of light as clouds break up and recede. Attending to the variability in light and its relationship to changes in weather would have been highly adaptive (Orians and Heerwagen, 1992).
- Signal of prospect and refuge. The sense of prospect is signalled by distant brightness and refuge is signalled by shadow (Appleton, 1975, Hildebrand, 1999). Brightness in the distance aids assessment and planning because it allows for information to be perceived in sufficient time for action to be taken. High prospect environments include open views to the horizon and a luminous sky (‘big sky’). A sense of refuge is provided by shadows from tree canopies, cliff overhangs, or other natural forms. Mottram (2002) suggests that allowing the eyes to rest on infinity (which the horizon represents visually) may be beneficial, even if the view is perceptually manipulated through visual images rather than actual distant views. Thus, our natural attraction to the horizon could be satisfied in many ways through the manipulation of light and imagery applied to vertical surfaces.
Photo: Gerry Johansson
- Signal of safety, warmth, and comfort. Although we usually think of the sun as the primary source of light in the natural environment, fire also served as a source of light and comfort, both physical and psychological. Anthropologist and physician Melvin Konner (1982) suggests that the campfire served important cognitive and social functions in developing human societies. The campfire extended the day, allowing people to focus their attention not only on the daily grind of finding food and avoiding predators but also on thinking about the future, planning ahead and cementing social relationships through story-telling and sharing the day’s experiences.
- Peripheral processing aid. Light also provides information about what is happening beyond the immediate space one occupies. It illuminates the surrounding environment that impinges continually on our peripheral processing system. The importance of peripheral light is evident from the discomfort many people feel when they are in a lighted space with low lighting at the edges, leading to a perception of gloom. Lighting researchers suggest that negative responses to gloom may be associated with its natural function as an early warning signal that visual conditions are deteriorating (Shepherd et al, 1989).
- Synchronisation of bio- and social rhythms. As a diurnal species, light plays a critical role in our sleep-wake cycles and also synchronises social activities. Although we can now alter our activity cycle with the use of electric light, research evidence nonetheless shows that night work is still difficult and often results in drowsiness, difficulty sleeping, mood disturbances and increased cognitive difficulties at work (Golden et al, 2005). Some night work facilities are using bright interior light to shift biological rhythms and increase alertness. There is also evidence that people who experience seasonally-related depression prefer to be in brightly lit spaces (Heerwagen, 1990).
Photo: Gerry Johansson
To summarise, light provides information for orientation, safety and surveillance, interpretation of social signals, identification of resources and awareness of hazards. Whether it is the changing colour of light associated with sunset or storms, the movement of fire or lightning, the brightness in the distance that aids planning and movement, or the sparkle of light off water – all these aspects of light have played a role in helping our ancestors make decisions about where to go, how to move through the environment, what to eat, and how to avoid dangers.