Demand characteristics and full spectrum lighting effects on performance and mood

Abstract Beliefs about full spectrum lighting were manipulated to test the hypothesis that demand characteristics, not lamp type per se , underlie the anecdotal reports of beneficial effects of full spectrum lighting on performance and mood. The dependent measures were reading, arithmetic, noun underlining, and mood. Subjects worked under either full spectrum or cool white fluorescent lamps. Under full spectrum lamps they were given one of three instruction sets: ‘Full spectrum lamps improve performance and decrease fatigue’ (positive set); ‘There is no evidence to support such claims’ (negative set); or neutral information about light. The participants in the cool white condition received only the neutral information set. The results showed that when existing beliefs about lighting are controlled, both positive and negative information about full spectrum lighting effects lead to improved reading performance and increased self-reported arousal. No effect of lamp type was found, confirming previous research.