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Greener equals cleaner: lessons from the streets of Copenhagen

Robert Hartnett, Senior Teaching Fellow

Faculty Blog

I don’t know how free from litter the streets in your town or city are, but in Copenhagen, Denmark, the streets are pretty clean. Indeed, the Danish capital is one of the cleanest in Europe. Mind you, this has not always been the case. There is a tendency towards littering in Copenhagen, but the City Council has an effective street and park cleaning service. Can more be done to keep Copenhagen’s environs clean?

In an experiment conducted by students of Roskilde University in Denmark in 2011 it was found that, by painting green footprints leading to a dustbin, littering was reduced by 43% in that area. What is going on here? Obvious, you might say: the footprints show where the dustbins are! Yes, but Robert Cialdini, in his book Influence: The Psychology of Persuasion, would classify the result of the experiment as an example of social proof in action. The rule of social proof is that we view a behaviour as more correct in a given situation to the degree that we see others performing it.

Credit to Pelle Guldborg Hansen, iNudgeyou and the group of students from Roskilde University, that made the original experiment.

Credit to Pelle Guldborg Hansen, iNudgeyou and the group of students from Roskilde University, that made the original experiment.

We know what happens when someone stands still and looks up in the air: sooner or later, others stop and stare too. The greater the number of people doing something, according to the rule, the more we believe that the behaviour is correct. It helps, too, if the people doing the action are like us.

Cialdini gives some examples of social proof:

  1. Canned laughter (a laughter track) causes viewers to laugh longer and more often. It is more effective on poor jokes.
  2. Bartenders seed their tip jars with a few coins to give the impression that tipping is the norm.
  3. The Jonestown Massacre – people followed each other to drink poison and committed a mass suicide. They were in a new place and just followed what fellow members (like them) did.
  4. Children learn more about their capabilities from other children than from adults.
  5. The Werther effect – a front-page suicide story leads to 58 more unusual suicides in the following month. Airline crashes are more deadly in that time frame as well.

Even if we do not see others doing the behaviour, the footprints are tangible social proof of the correct thing to do: bin it!