One of the most effective way to steer people toward good or bad behaviour is via social influences.

According to social norm theory, our behaviour is influenced by observing the behaviours of the people we’re surrounded by. When large portion of a society holds a certain attitude, it is likely that each individual will adopt it as well. For instance if everyone in a meeting holds a certain view or accepts a certain proposition, we might conclude that they are probably right. If we see people socialising in a certain way at a get-together, we tend to behave in a similar way.

There are two types of social influences. The first involves information. If a group thinks or does something, their thoughts and actions convey information about what might be best for you to think or do as an individual. The second involves peer pressure. If you’re affected by what people think about you, you’ll most likely follow them to avoid their disapproval. The latter type of social influence is most effective when it comes to getting long-lasting results.

Various recent studies have documented the impact of social influence upon individuals’ engagement in sustainable behaviour. In an experiment by professor emeritus of psychology and marketing at Arizona State University Robert Cialdini, social influence was used to encourage hotel guests to reuse their towels. A sign was placed in rooms to inform guests that more than 75 per cent of previous guests had reused their towels in that exact room. This resulted in a staggering 49.3 per cent increase in towel reuse.

The basic setup and results for Cialdini’s towel reuse experiment.

The basic setup and results for Cialdini’s towel reuse experiment
Image via iNudgeYou

In another example, students at Roskilde University in Denmark experimented with social influence to reduce unnecessary energy usage on campus.  The students aimed to reduce the number of lights that were left on in rooms across campus after everyone left. The lights were often left on as a result of habitual routine, not due to some conscious decision. Students often forgot to switch off the lights as they were busy attending to a number of tasks while leaving the room, such as packing their bags, picking up their trash or checking the train or bus schedule.

This issue informed the design and installation of a green poster with a drawing of a hand giving a thumbs-up, which was directed at a light switch. The poster had a written sound effect saying “Klik” to draw the students’ attention to the light switch as they were leaving the room.

In addition, text saying “More than 85 pct. of the students at Roskilde University remember to turn off the lights. Do you?” was put at the bottom of the poster. This social influence strategy proved an effective tool for changing students’ behaviour. The “Klik” intervention resulted in a 26.4 per cent reduction in the amount of lights left on.


Social influence should be visible and clearly communicated, preferably by direct contact to the target audience. Programs to promote sustainable behaviour should attempt to communicate what is acceptable and what is unacceptable behaviour. Bankstown City Council’s highly commended “Recycle Right Program” employed various persuasion strategies to encourage proper recycling among 1,400 households, lowering the number who recycled improperly from 30 per cent to 15 per cent in three months.

The council aimed to discourage the incorrect disposal of plastic bags in recycling bins. Key strategies included giving residents a collection tub to discourage the use of plastic bags to carry recycling from their units to the bin, and replacing bin lids with a small hole to make dumping whole plastic bags in the recycling bin inconvenient.

Of all the strategies employed, personalised feedback was found to be the most effective. This involved  officers randomly inspecting residents’ yellow bins before collection and giving feedback as to how well they have recycled in comparison to other households. Officers placed feedback cards with a smiley face or a frowning face on residents’ door handles, letterboxes and bins indicating whether they did a good job of recycling or need to do more. These cards were effective as residents did not want to break the social norm. A film of the program and its findings is available here.



The above case studies clearly demonstrate that social influence is an effective tool to persuade people to act in better ways. Humans are influenced by other humans. We’re more likely to conform when we’re aware of what others would think or say about us if we acted in non-conforming ways. Designers of sustainable built environments, products and programs should creatively use this insight to nudge people toward the desired behaviours.