Darkness encourages unethical behaviour even when it makes no difference to anonymity

Imagine a man sits alone, hunched over his desk, fingers tapping out a project progress report to his boss. Does he decide to lie? If I told you that the sun had nearly set, filling the man's room with darkness, would that make any difference to your answer? It should do. A new study suggests that darkness encourages cheating, even when it makes no difference to anonymity.

Chen-Bo Zhong and colleagues had dozens of undergrad students complete a basic maths task against a time limit. Afterwards they had to fill in an anonymous form indicating how many items out of twenty they'd answered correctly and they had to take a monetary reward from an envelope (up to twelve dollars) in line with their performance. Half the students completed the task in a dimly lit room (though still light enough to see each other) whilst the other half completed the task in a bright room.

A surreptitious coding system allowed the researchers to match up the students' self-completed scoring cards with their actual performance. You guessed it, the students in the dimly lit room tended to exaggerate their performance more than the control group in the bright room (by an average of 4.21 items vs. 0.83 items). Another way of looking at it is that 60.5 per cent of participants in the dim room exaggerated their performance compared with just 24.4 per cent of participants in the bright room.

In the same way that young kids think they are invisible when they cover their eyes, Chen-Bo Zhong's team think the effect they observed occurs as an automatic response to the cover of darkness, even when the lack of light makes no difference to anonymity.

A second study supported this interpretation, finding that student participants wearing sun-glasses chose to share money less fairly in a computer-based economic game than did students wearing normal glasses. Again, the subjective reduction in light made no difference to actual anonymity as the game was played entirely via computer with a partner who participants thought was in another room. The students who said they felt more anonymous tended to share the least money, thus suggesting that perceived anonymity was mediating the effect of darkness on behaviour.

'Darkness appears to induce a false sense of concealment, leading people to feel that their identities are hidden,' the researchers said. The next time you're deliberating over a moral issue, you might want to think about whether you've got the lights on or not!
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Zhong, C., Bohns, V., & Gino, F. (2010). Good Lamps Are the Best Police: Darkness Increases Dishonesty and Self-Interested Behavior. Psychological Science DOI: 10.1177/0956797609360754