This research project aims at investigating how indoor lighting influences motivation. More specifically, the project is concerned with effects of light’s correlated color temperature on effort intensity during a cognitive task performance. Cool white light that includes more blue spectrum components has a higher alerting function (Brainard, 2002). As main hypothesis, I predict that in comparison to warm white (with more red components) light, cold white (with more blue components) light should induce higher alertness state which should increase effort intensity through its effects on experienced task demand, according to motivational intensity theory (Brehm & Self, 1989). The main dependent variable-effort-is defined as resource mobilization to perform instrumental behavior. Effort will be quantified as changes in beta-adrenergic sympathetic nervous system impact on the heart (Richter, Friedrich, & Gendolla, 2008; Wright & Kirby, 2001). Previous research on non-visual lighting effects investigated chronobiology, circadian rhythms, sleep, wellbeing, mood, stress, visual comfort, productivity (van Bommel, 2006) whereas no research focused on effects on motivation or effort, which is the aim of this project. Moreover, the results of this project will have a practical application, especially in designing environments for various achievement contexts like education and office work.