When someone enters a building, what predicts whether or not they will hold the door open for a stranger behind them? New research published last month in the journal Psychological Science finds that one major factor is whether the door holding is likely to result in the expenditure of less total effort than if each person had to open the door on his or her own. As it happens, we have an unconscious desire to reduce the work for groups of people interacting together. This desire can drive our etiquette.

To show how, sometimes, politeness is influenced by the aspiration for group effort reduction, psychologists Joseph Santamaria and David Rosenbaum videotaped roughly 150 people walking through the student union building at Penn State University. They later examined the tapes to review people's door-holding behavior.

It's a common assumption that the odds of someone holding a door open for those behind them is all about the physical distance between two people: If you reach a door first and someone is right behind you, you hold it open. If they are farther away, you don't. But it turns out that distance isn't the entire story. Instead, our unconscious is all about conserving the energy of groups of people—and this influences how long we hold the door.

The researchers found, for instance, that the first person to reach the door was more likely to hold it longer if two rather than one person followed behind. If it was just about distance, one versus two followers shouldn't matter. But, if we unconsciously try to reduce the effort that others have to expend, then it makes sense to hold the door longer when you see several people approaching. The end result is that fewer people have to exert energy to open the door themselves.

The researchers also found that when a follower noticed that the door was being held open for them, they quickened their pace. Yes, speeding up does mean more effort for the follower, but it also reduces the effort of the holder and thus increases the likelihood that the joint effort of both the holder and follower will be less than if each had acted on their own.

This unconscious desire to minimize energy expenditure is not limited to door holding. It plays out in all sorts of situations. Next time you are sitting at dinner and your companion asks you to hand them a fork, for example, reflect for a moment on how you did this. You likely handed it to them in such a way as to minimize the amount of hand rotation they had to produce to grab it. Being polite, it turns out, has a lot to do with saving others energy—even more evidence, as I have blogged about before, that our body has a strong influence on our mind.

Santamaria, J. & Rosenbaum, D. (2011). Etiquette and Effort: Holding Doors for Others. Psychological Science.

For more on connections between the mind and body, check out my new book Choke!

Follow me on Twitter!

Recent Posts in Choke

Can Daily Hugs Help Prevent Common Colds?

Life’s tension increases risk of infection; hugs help heal us.

Your Body Knows Its Mind

Viewing the mind and body as connected has health benefits

How Your Partner's Personality Impacts Your Career Success

What happens in your kitchen affects what happens in your office.

Morality Is Contagious

How we behave depends on how others treat us.

When Talent Backfires

Too much talent can break teams apart

Can You Trust Your Memory?

A new study shows we can sometimes remember things that never happened.