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Positive Social Proof - Behaviour Change Made Easy


They're common in almost all workplaces, the sign telling people to turn the lights out when they leave a room or the e-mail bemoaning the mess in the kitchen. 

But what's written on that sign or in the e-mail can have a significant impact on how effective it is and whether it has a positive or a negative impact.

A classic study of the effect of signage on behaviour was carried out in the Petrified Forest National Park in Arizona in the US and shows just how easy it is to get it wrong.  The park contains beautifully fossilised wood and animal bones that are scattered around the dried canyons, which are subject to theft.

To test the effects of different signs a group of researchers installed two different signs in two areas of the park as well as leaving one area with no signs to act as a control.  They then secretly marked pieces of wood in all three areas so they could measure the level of theft.  The signs read:

  1.  "Many past visitors have removed the petrified wood from the park, changing the natural state of the Petrified Forest." This sign was accompanied with a picture of several people taking pieces of wood. 
  2. "Please don't remove the petrified wood from the park, in order to preserve the natural state of the Petrified Forest." This sign was accompanied by a picture of a single person taking a piece of wood with a red circle and bar over their hand.

So what were the results?  Well, in the area with no signage 2.92% of the marked pieces were stolen. In the area with the second sign, which just asked people to leave the wood alone, 1.67% of pieces were stolen. While in the area with the first sign, which highlighted that theft was a problem, a whopping 7.92% of pieces were stolen. 

Promoting Bad Behaviour

Rather than preventing theft the wording of that sign almost tripled the rate of theft, it turned into a crime encouragement message!

Why did this happen?  Basically, the wording of the first sign reinforced the bad behaviour by clearly communicating that it is the social norm, it's what everyone else is doing.  It points out that the bad behaviour is common and it encourages some people to think 'everyone else is doing it, I'd better get my piece too.' 

Avoiding the Negative Social Norm

So what's the lesson here?  How does signage in a national park relate to the workplace?  Put simply, whether the sign is about saving energy in the office or looking after a natural location we, as a group, respond in similar ways. We take many of our cues from the people around us. So when you're sending a message about the behaviour you want to see it's important to send and reinforce the right cues. 

When writing a sign or an e-mail:

  • Highlight the behaviour you do (or don't) want to happen. Something like 'Thanks for keeping the kitchen tidy,' is going to be more effective than 'Stop leaving the kitchen in a mess - clean up after yourself" (as pictured). This second message just reinforces that everyone is leaving a mess. 
  • If possible re-frame the numbers to support a positive social norm rather than a negative one. In the case of the Petrified Forest only 2.9% of all the park visitors take any of the wood.  So maybe something like 'More than 97% of all visitors help preserve the park by leaving the wood on the ground."  In the workplace you could frame a message along the lines of 'Most people remember to turn the lights off when they leave the room." This message reinforces the social norm and encourages other to follow suit.

It can be difficult to frame something positively - especially if you get annoyed walking into a room with all the lights still on - but focus on encouraging the right thing, rather than highlighting the negative norm. Reinforce the idea that most people are doing things the right way.

More Information

For more tips on the writing effective signs see Sending the Right Signs article, part of our Behaviour Change Made Easy series.

Reference: Yes, 50 Secrets From the Science of Persuasion N Goldstein, S Martin, R Cialdini

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