Correction Appended: March 3, 2010
Human beings can be a devious lot. At some point, even the most moral of us have skulked or sneaked or filched something we weren't supposed to even if it were just a cookie from the kitchen. Of all the things that get our sneakiness juices going, there is nothing like a little darkness.
There has always been a correlation between how ethically we behave and how brightly our surroundings are lit most evil deeds are done under cover of darkness, and the rarest and most brazen crimes are those committed in broad daylight not least because we're less likely to be caught in the act after nightfall. But in a new study published in the journal Psychological Science, psychologists Chen-Bo Zhong and Vanessa Bohns of the University of Toronto and Francesca Gino of the University of North Carolina suggest that it's not only about the threat of discovery. There are other reasons darkness gives us a waiver to misbehave.
The investigators already knew that throughout our lives, we have a sometimes distorted sense of the ability of darkness to conceal. Toddlers cover their eyes when they're playing hide and seek in the belief that if they can't see you, you can't see them. In his famed 1969 experiments on human moral behavior, Stanford University psychologist Philip Zimbardo found that if subjects were wearing dark hoods and baggy clothes, they were more inclined to administer electric shocks to other volunteers than they otherwise would be.
In the new study, Zhong and his colleagues took a subtler approach, but one that's likely to have more real-world implications. In the first part of their three-part experiment, they recruited 84 students and divided them between a brightly lit room with 10 fluorescent bulbs burning and a dimmer room with only four bulbs. The subjects were each given a brown envelope with $10 in singles and coins as well as an empty white envelope. They were all then told they had five minutes to complete a simple mathematical task, looking for pairs of numbers that added up to 10 in a grid of three-digit numbers. They could keep 50 cents for every pair they found and were to put the leftover money in the brown envelope.
When the researchers collected the envelopes and reviewed the results at the end of the five-minute period, what they found was striking. Consistently, the people in the dimmer room reported finding more matches an average of 11.47 than those in the bright room, who averaged just 7.78. When their work was checked, it turned out that cheating was rife in the dim room, with the participants there claiming an average of 4.21 more correct answers than they actually got, compared with 0.83 for the other room. Even though none of the subjects put their name on their paper and all were thus anonymous, the darkness still seemed to confer what the researchers called a "false sense of concealment," and that in turn created an additional "licensing effect."
In the second experiment, 50 students were similarly divided into two groups, this time in equally bright rooms, but one group was given sunglasses to wear and the other glasses with clear lenses. Each volunteer was then placed before a computer and told to interact via chat only with a partner in another room, who was actually one of the researchers. The volunteers were given $6 to divide any way they wanted between themselves and their partner. There was no question of honesty on the line keeping the entire $6 and giving the partner nothing was a permissible choice but there were questions of generosity and fairness, and once again, darkness made a difference. Participants who wore sunglasses gave an average of $1.81, compared with $2.71 for the other group.
"[The] participants did not expect to see or talk to the recipient of their offer before or after the experiment," the researchers wrote. "Nevertheless, darkness increased self-interested behavior."
In the final part of the experiment, Zhong and his colleagues re-ran the sunglasses test, but also asked the participants to complete a questionnaire in which they agreed or disagreed on a 1-to-7 scale with statements like "I was anonymous during the study," "I was watched during the study" and "Others were paying attention to my behavior during the study." Again, the people wearing sunglasses scored significantly higher on the perception of anonymity study, even though they all rationally knew the glasses made no difference.
There are a number of evolutionary explanations for the participants' behavior and a number of practical implications. We evolved in a world with a day-night cycle and as a practical matter, darkness does conceal behavior, so it's no surprise that that protected feeling lingers in the unconscious whenever the lights go down. What's more, humans are notoriously egocentric, and we have a hard time remembering that the rest of the world doesn't always perceive things the way we do. That's the reason that in psychological tests, children in the 4-to-7 age group mistakenly believe that a doll seated facing them would see the room the same way they do, instead of from the opposite perspective. It's also the reason that in adulthood, we tend to overestimate the ability of others to notice when we're nervous or distracted, simply because we feel that way. Says Zhong: "We believe this behavior is learned through our early experiences with darkness and also our egocentric biases."
Zhong and his colleagues do not recommend flooding trading floors or K Street lobbyists' offices with light in order to enforce ethical behavior at least not yet. But they do speculate that even when we communicate via e-mail, we may be more inclined to lie or distort if the lights are low than if the room were filled with sunshine. Perhaps the next time you or your kids sit down at the computer to chat or text, it's best to raise the blinds and insist that the person on the other end do so too.
The original version of this story misidentified the gender of researcher Chen-Bo Zhong, who is male.