Light, whether natural or artificial, has physiological and psychological effects on human beings. For example, adequate exposure to the sun can increase the physical and emotional well-being of a person. Physiologically, light is known to influence bodily processes that regulate the most fundamental functions of the body, signifying just how potent an effect ithas on health. The circadian rhythm adjusts to the environment through external cues, the most important of which is daylight. Exposure to artificial light during the wee hours can trigger chemical changes and hormonal emissions that could cause an imbalance.
If this persists, the immune system can weaken and various health problems may result. Skin flare-ups, migraine headaches, sleep disorders, cataracts and macular degeneration, cardiovascular disease and even cancer are just some of the conditions that can be caused or worsened by too much or too little light or exposure to light at the wrong time.
While much investigation into the physiological effects of light has been carried out, little has been done on the potential it has to affect the mood or temperament of a person. Indeed, the scientific community was initially unconvinced about light’s mood-altering capacities. However, published studies on this subject have persuaded researchers of the validity of examining the effects of light on emotion.
For example, studies on seasonal affective disorder (SAD) have revealed that SAD is not some unusual malady experienced only by few individuals but rather a recurring major depressive disorder that is fairly common and that occurs at specific times of the year, particularly summer and winter, and then abates as the season changes. Sufferers experience similar symptoms, including oversleeping, fatigue and depression. Once SAD was accepted by the medical community as a true disorder, effective treatments were sought, such as light therapy and melatonin supplementation.
Apart from research on SAD, studies on the connection between light and human emotions have been scant. The most recent inquiries involve colour composition and brightness of light and their immediate effects on the emotional state of a person. In the former, researchers hypothesized that light acutely influences emotion even during short-term exposure. This was a compelling point because previous studies had concluded that light has an impact only after exposure has occurred over an extended period of time. The research on colour composition proved this to be untrue.
Colour elicits emotional reactions in people, a phenomenon considered to be partly a result of cultural learning. In some countries, white is the color of innocence, but in others, it is the color of death. Some studies, however, explain that these reactions are innate rather than learned. For example, the colours yellow, red, blue and green evoke certain responses in most people—red is stimulating, green is calming, and so on. It would stand to reason, then, that coloured light would also bring out an emotional reaction.
In separate studies conducted at research centers in Belgium, Switzerland and England, researchers ascertained that the colour of light influences the way emotional stimuli are processed by the brain. Certain cognitive tasks routinely increase activity in specific parts of the brain whereas other activities can decrease activity. When activity increases, the activity is said to have an impact on the functional organization of the brain.
In the coloured light experiments, volunteers listened to angry-sounding voices and neutral-sounding voices while exposed to alternating periods of blue and green light. Brain activity was recorded by magnetic resonance imaging. When the volunteers were subjected to ambient blue light, responses to the angry voices increased in the hippocampus, the amygdala and that part of the brain where voices register. This indicated the functional connectivity of these parts of the brain that decode vocal information. The results thus supported the assumption that even brief exposure to blue light can have a profound impact on how the brain processes emotional stimuli, activating and strengthening the connections between areas of the brain that process language and emotions.
Research on light intensity has also been sparse. The means for substantiating the effects of bright light on mood were not available. Moreover, response to light appeared to be highly personal and depended on experience and cultural influences. Some early research deduced that it was also based on gender, with women preferring dimly-lighted places and men preferring brightly lighted ones. A study conducted at the UTSC this year was premised on the theory that simply turning on the light can rouse a human being’s emotional system.
The main researcher, Alison Jing Xu, conducted six studies and demonstrated that human emotions—both positive and negative—are felt more intensely when a person is under bright light. Bright light is perceived as heat, and heat is known to trigger emotions. In Xu’s experiments, no matter what the stimulus was, bright light had the capacity to intensify a person’s emotional reactions.
Participants were exposed to different lighting conditions and then asked to respond to different types of stimuli, such as a spicy sauce, negative words, positive words, a fictional character, the appearance of a person, and two kinds of juices. It was noted that the brighter the lighting, the more emotional the response was. The participants were more likely to ask for more spicy sauce, have extreme reactions to both positive and negative words, have more aggressive feelings toward the fictional character, rate a person as being much more or much less attractive, and drink more of the juice that they thought was tastier.
The results of the research have ramifications for various types of situations. For example, if a business establishment wanted a stronger reaction to a new product, it would be to their benefit to conduct a product launch in a brightly lighted place. If a person was about to give bad news and wanted to tone down an individual’s reaction to the news, it would be good to dim the lights.