Light is essential for visual perception i.e., our ability to interpret our surrounding environment through the light that enters our eyes.   Behavioural lighting research documents positive influences of light and colour on physiology and moods (Gerard, 1958; Küller, Ballal, Laike, Mikellides & Tonello, 2006). This article, which is mostly based on the work in my doctoral thesis, which explored the design and development of a bidirectional activity-based ambient lighting system to improve communication between the elderly and their caregivers. I will discuss the physiological effects of light and colour as well as I will explore the behavioural effects of light. Finally, I will provide an overview of the lighting design dimensions to be considered when designing ambient lighting interventions for assisted living environments.

Physiological Effects of Light

Cajochen (2007); Yasukouchi and Ishibashi (2005) demonstrate that light can affect various physiological aspects such as:

• alertness,
• arousal levels,
• body temperature,
• sleep, and
• circadian rhythm.

Melatonin and Cortisol on Circadian Rhythm

Notably, both melatonin (i.e., hormone that regulates sleep) and cortisol (i.e., an adrenal hormone released in response to stress and low blood-glucose concentrations) play critical roles in assessing the effects of light on circadian clock disruption (Cajochen, 2007), which may cause depressive symptoms and poor sleep quality. Furthermore, Thapan, Arendt and Skene (2001) state that short-wavelength light (blue light) is known to suppress melatonin levels. 

Melatonin suppression can be relieved by deploying longer wavelengths of light toward yellow, orange and red (Pauley, 2004). Moreover, bright light therapy has been proven to alleviate symptoms associated with mood and sleep disorders (Shikder, Mourshed & Price, 2012).

Psychophysical Effects of Colour

Brightness, saturation and hue have been shown to have positive effects on emotions. For example, Jacobs and Hustmyer (1974) deduced the following from physiological measurements such as galvanic skin response, heart, and respiration rates.

Colour associations with emotions

• Red is remarkably more arousing than either blue and yellow.
• While green induces greater arousal levels than blue.
• Additionally, by using the pleasure, arousal, and dominance scale, Valdez and Mehrabian (1994), have found hues such as blue and blue-green evoked more pleasant feelings.
• While yellow and yellow-green were least pleasant.
• Red was ranked at an intermediate value of pleasantness. Similar pleasantness ratings were obtained by Kwallek, Woodson, Lewis, Sales et al. (1997), which investigated the impact colour on mood and worker performance.

Another case in point is illustrated by Gerard, who while using psychophysiological measures reported that the higher arousal levels associated with red are triggered by unpleasant associations of red light with the following:

• blood,
• injuries,
• fire,
• aggression,
• and danger.

 Whereas the low arousal levels associated with blue are induced by the association of blue with the following (Gerard, 1958).

• serenity,
• the skies,
• and friendliness.

Conflicting impacts of the colour red on psychological behaviour are demonstrated by Hevner (1935) where red is associated with happiness and excitement. In addition, Ou, Luo, Sun, Hu and Chen (2012) demonstrated affective implications of lighting colour using colour emotion scales such as “passive” or “active”. The more reddish the colour yielded the more “active” colour emotion response by both elderly and younger adults while higher variations of blue were in most instances ranked as more passive by both user groups. Essentially, Olsen (2010) argues that the meaning of colour is based on ‘learned associations’ coupled with the physiological responses. Moreover, varied interpretations of colour are heavily reliant on culture, age, and situational context.

How does light make you feel?

Added to the physiological effects, many researchers have accrued evidence that light can affect the following. 

• well-being (Kuijsters, Redi, de Ruyter & Heynderickx, 2015),
• interpersonal communication (Gifford, 1988),
• social and emotional functioning in older women (Grandner, Kripke & Langer, 2006),
• improved performance on a variety of cognitive task and interpersonal behaviour (Baron, Rea & Daniels, 1992),
• time estimation (Delay & Richardson, 1981) and
• creating an inviting and pleasant atmosphere (Custers, De Kort, IJsselsteijn & De Kruiff, 2010).

In contrast, other scientists have failed to identify significant influences of light on moods (Baron et al., 1992; Knez, 2001) and a variety of cognitive tasks (Boray, Gifford & Rosenblood, 1989; Veitch, 1997).

Designing with Light and Colour in Ambient Assisted Living Environments

Altogether, a general inference can be drawn on the potential influence of light, especially coloured light on interpersonal relationships, mood, and performance on various cognitive tasks. Still, a deeper understanding of the implications of coloured lighting is needed to facilitate the design of intelligent lighting interventions in assisted living environments. For example, if we consider lighting designs for older adults, the majority of lighting experiments were conducted with relatively young people aged 18−35 years as discussed by Kuijsters, Redi, de Ruyter, Seuntiëns and Heynderickx (2015). Thus, the vision problems of older adults, which influence their perception of light are often overlooked. Despite these challenges, light’s non-visual effects could be advantageous especially for elderly people, who tend to struggle with alertness and loneliness. Therefore, the design dimensions discussed by Philips Research (2008) such as variations in: 

• brightness,
• colour rendering,
• direction,  and
• patterns

could enhance user experience in elderly research exploiting ambient lighting. In essence, light’s aesthetic qualities along with its dynamic properties present an opportunity to explore how coloured lighting can be integrated into ambient assisted living environments. 

Further readings

To learn more about the design and development of an ambient lighting intervention to support social connectedness between the elderly and their caregivers, you may refer to the following papers.

1. Davis, K. A. (2017). Social hue: a bidirectional human activity-based system for improving social connectedness between the elderly and their caregivers. Technische Universiteit Eindhoven.
2. Davis, K., Owusu, E. B., Marcenaro, L., Feijs, L., Regazzoni, C., & Hu, J. (2017). Effects of ambient lighting displays on peripheral activity awareness. IEEE Access, 5, 9318-9335.
3. Davis, K., Owusu, E., Marcenaro, L., Feijs, L., Regazzoni, C., & Hu, J. (2016, December). Evaluating human activity-based ambient lighting displays for effective peripheral communication. In Proceedings of the 11th Eai international conference on body area networks (pp. 148-154).
4. Davis-Owusu, K., Owusu, E., Marcenaro, L., Regazzoni, C., Feijs, L., & Hu, J. (2019). Towards a deeper understanding of the behavioural implications of bidirectional activity-based ambient displays in ambient assisted living environments. In Enhanced Living Environments (pp. 108-151). Springer, Cham.

Check out a few related articles here:

1. Perception, Attention, and Memory for Social Connectedness in Mediated Environments

2. What you need to know about Social Connectedness

3. Reflections on Ageing in the Eastern and Western Hemisphere – Excerpts from my PhD. journey

References

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