According to a new study, people who spend more time in natural lighting than in artificial lighting have increased productivity and alertness. Light directly influences the amount of melatonin a person produces, which indirectly affects alertness. “Most people spend their days within buildings under different lighting environments, which range from daylight to artificial light only,” said Mirjam Münch of the Solar Energy and Building Physics Laboratory at the Swiss Federal Institute of Technology in Lausanne, Switzerland. “At most workplaces, there is a mixed situation between the two principal light sources.” Münch added, “For the impact of light perception on nonvisual functions such as alertness, mood, and performance, those lighting conditions are likely to significantly contribute to modulation of alertness and productivity via the retinohypothalamic tract and melanopsin-dependent pathways.” Because few studies have examined the effects of lighting on cognitive performance, Münch and her colleagues conducted a study to determine how natural and artificial light affected cognitive functioning in the evening.
Participants between the ages of 19 and 25 years old were exposed to daylight (DL) or artificial light (AL) for six hours a day for two days. Each evening, after the exposure, the researchers evaluated melatonin and cortisol levels, and rated sleepiness and cognitive functioning and found significant differences in the participants. “Subjects felt significantly more alert at the beginning of the evening after the DL condition, and they became sleepier at the end of the evening after the AL condition,” said Münch. “On their first evening, subjects performed with similar accuracy after both light conditions, but on their second evening, subjects performed significantly more accurately after the DL in both n-back versions and committed fewer false alarms in the 2-back task compared to the AL group.” Münch added, “In summary, even short-term lighting conditions during the afternoon had an impact on cognitive task performance in the evening.” She added, “Such a relationship could be crucial for workers requiring high attention levels and executive functioning, such as bus drivers, industrial workers in sensitive areas, or air-traffic control.”
Münch, M., Linhart, F., Borisuit, A., Jaeggi, S. M., & Scartezzini, J.-L. (2011, December 26). Effects of Prior Light Exposure on Early Evening Performance, Subjective Sleepiness, and Hormonal Secretion. Behavioral Neuroscience. Advance online publication. doi: 10.1037/a0026702
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