Bright white light conditions have been found to have a positive effect on working memory performance. In order to investigate this effect, 24 participants were presented with two triplets of white light conditions that have a fixed illuminance (either 60 or 300 lx), an identical color temperature (~4100K), and the same cone activation, but a different level of ipRGC activation. The light conditions lasted for 4 minutes and were preceded and followed by 2.5 minutes of darkness and 2 minutes of dim light, equivalent to the lowest melanopic EDI condition. During each of the conditions, working memory performance was measured by a 2-back task, for which the reaction time and accuracy were tracked. The participants also filled in the ultra-short version of the Munich ChronoType Questionnaire to test if the performance is also influenced by circadian effects or the number of hours since waking up. Multilevel regressions were used to analyze the data. The results found no significant effect of melanopic EDI or intensity on the performance in the 2-back task. However, the change from high to low illuminance was associated with lower reaction times. Moreover, the number of hours awake leads to lower accuracy in the high light intensity (300 lux) conditions. However, the model used for the last analysis violated two assumptions, therefore it is uncertain if these effects are generalizable. More research, ideally with larger sample sizes, is needed to conclusively determine these findings.
Experiencing metameric light
Rădulescu, R. (Author). 2022
Student thesis: Bachelor