Firstly, participants were asked to split 160 Taiwanese dollars between themselves and someone in another room. Participants in a well-lit room offered, on average, $69.60, whereas those in moderately- and dimly-lit rooms offered $58.60 and $47.40 respectively. In a twist, all were overpaid by $50. Though 85 percent of those in the well-lit room returned the money, that fell to 70 and 52 percent in the moderately and dimly-lit rooms.
In another test, participants were shown 'morally resonant' words printed in white or black and asked to identify the colour. Reaction times for positive words were faster than for neutral words when they were printed in white, but slower when they were printed in black, and the effect was greater under brighter light. They were also invited to make donations to the lab on their way out. On average, $41 was donated in the brightest room, decreasing to $28.60 and $19.30 at lower brightnesses.
Finally, different participants were invited to volunteer to help a grad student code up some data sheets. In the brighter room, 5.9 sheets was the average volunteered, compared to 4.3 in the dimmer room.
Although it's tempting to think that those in the dimly lit rooms sensed a veil of darkness under which they can get away with proverbial murder, the researchers reject this explanation. Instead they believe there's a subconscious link between brightness and morality. Neurochemists might offer alternative explanations.
The paper, by Wen-Bin Chiou and Ying-Yao Cheng of the National Sun Yat-sen University, will be published in a forthcoming issue of the Journal of Environmental Psychology.