Water conservation is one of the major challenges of the 21st century. The world population is growing fast, but the global water resources stay the same. How can we use behavioural science to make water consumption more sustainable?

The nudge theory demonstrates that small adjustments to the environment can heavily influence people and make them more likely to choose the desired course of action. One of the most effective behavioural nudges which can be applied in the context of water conservation is the social proof heuristic. It is the fact that our perception of what is acceptable or correct depends on what other people do or believe in. Beliefs and behaviour of other people represent the “proof” supporting the action or belief. The more people engage in a given behaviour the stronger the “proof” is. This insight has been widely applied in business and social policy by delivering messages such as:

“Nine out of 10 people in the UK pay their tax on time.” This and other nudges used by HMRC increased tax revenues by £210m.


“Nearly 3/4 of hotel guests choose to reuse their towels each day.” In this example, the number of replaced towels dropped by 17%.

We can use this insight in the water conservation context by delivering a similar message relating to how many people save water. More effective variants of the message involve personalisation – the more personally relevant the message is, the better (e.g. using the name of the recipient multiple times and his or her town, local community, post code or neighbours as the reference point for water usage).

In Cape Town, where water shortages are particularly severe, the local water supply company shows maps with water usage by house. Here people can easily compare how much water they consume and how it relates to others. It also taps into the competition heuristic, which is the fact that we get extra motivation to act if the action is framed as being part of competition with others. The power of this heuristic can be seen in many websites such as Viagogo, eBay or Booking.com which deliver messages suggesting that users should quickly buy a product before it’s taken by somebody else. Parents also use this strategy – instead of shouting on their children to sit quetly, they frame it as a competition between them: “which one of you will be able to stay quiet for longer?”.



Another behavioural nudge that we can apply here is cognitive saliency. Cognitive saliency is a measure of how easily accessible given information is in our brains. The more salient a given concept is the more strongly it can influence thinking and behaviour. To build saliency of the water conservation problem we can visualise the amount of water customers use by for example inserting a picture of a dozen barrels or a small pool in a dedicated letter or a bill. This can be then compared with 10 barrels that our neighbours use on average. Increasing the saliency of the water we consume will motivate people to be more careful.

Finally, the conventional wisdom says that people are rational actors who will be most effectively influenced by facts and figures. Talking about how we are slowly destroying our planet is supposed to prompt customers to do some soul searching and reconsider their water habits… A large body of evidence, however, has shown that this view is flawed as people are more influenced by seemingly irrelevant factors. Rational arguments, however, can be effective by working in conjunction with behavioural nudges. People are motivated by the nudges, but then they feel obliged to invent post hoc rationalisations of their behaviour. Although we aren’t perfectly rational, we want to see ourselves as rational. By delivering relevant facts and figures we can facilitate the post-rationalising process and further reinforce the conservation behaviour.


Darius Lucas - Behavioural Analyst

Author:Darius Lucas - Behavioural Analyst

Darius Lucas is a psychologist specialising in behavioural science and neuroeconomics. His main role in behave is generating behavioural insights for strategy and media campaigns. He joined Behave after completing his MSc in Psychological Research at Oxford.