Recently I was travelling for business and was looking at the little sign in the bathroom that said something like “HELP SAVE THE ENVIRONMENT – You can show your respect for nature and help save the environment by reusing your towels during your stay”.

It got me wondering – do these little signs actually work?

So I went looking for evidence and found the surprising answer. In the process I also came across a powerful force identified in behavioural science that could make these signs 50% more effective.

I found the answer in an experiment undertaken by a team of researchers who conducted a large-scale experiment in a major hotel. Over a period of 80 days they undertook a study across 190 rooms with the guests being unaware they were participants in a study.

THE EXPERIMENT

The researchers tested three different messages that aimed to influence the guests to participate in the towel reuse program.

The standard environmental control message stated, ‘‘HELP SAVE THE ENVIRONMENT. You can show your respect for nature and help save the environment by reusing your towels during your stay.’’

The second message offered an incentive to the guests to participate stating, ‘‘PARTNER WITH US TO HELP SAVE THE ENVIRONMENT. In exchange for your participation in this program, we at the hotel will donate a percentage of the energy savings to a nonprofit environmental protection organisation. The environment deserves our combined efforts. You can join us by reusing your towels during your stay.’’

The third message stated, ‘‘WE’RE DOING OUR PART FOR THE ENVIRONMENT. CAN WE COUNT ON YOU? Because we are committed to preserving the environment, we have made a financial contribution to a nonprofit environmental protection organisation on behalf of the hotel and its guests. If you would like to help us in recovering the expense, while conserving natural resources, please reuse your towels during your stay.’’

At the bottom of each message were instructions on what to do: “If you choose to participate in the program…Please drape towels over the curtain rod or on the towel rack. If you choose not to participate in the program…please place towels on the floor.” They also added information about the benefits to the environment when people participated.

The different messages were randomly distributed across the 190 rooms.

One of these messages increased participation in the towel reuse program by 47%. Which message do you think it was?

WHAT BEHAVIOURAL SCIENCE TELLS US

Incentives

Both the control message and the second message are trying to influence the guests by offering an incentive. The control message is providing an incentive in the form of social motivation that might make the guests feel good about their decision or perhaps less guilty about their impact on the environment.

The second message, in addition to the social motivator to help the environment is also offering an incentive in the form of a financial donation if the guest participates in the towel reuse program.

According to Dan Ariely, who is a professor of psychology and behavioral economics at Duke University, some incentives do not work well together. In particular, incentives associated with financial motivations do not work well with social motivations because it results in what is known as crowding out

Use incentives with care. Mixing incentives is a bit like chemistry – put the wrong elements together and you can end up with an undesirable outcome.

Consider the following scenario: Imagine I ask you for a favour to help me move something heavy like a piece of furniture. How likely would it be that you would help me because you would feel good about it?

Now imagine I asked you to help me to move the furniture but this time I said I would pay you $2. What would happen to your motivation to help me then? Would you still feel good about helping me and as a bonus you would get $2 or would you feel less motivated to help? What is likely to happen is that the financial incentive would crowd out the social incentive and you would now see the task as work and wouldn’t be as interested making you less motivated to help.

Reciprocity

The third message states that the hotel has already donated to a “nonprofit environmental protection organization” on behalf of the guest and asks them to help by reusing their towels.

This message employs the rule of reciprocation which says that we should try to repay, in kind, what another person has provided us. It is a well-established social norm and a strong determining factor in human behaviour. So much so that society assigns socially punishing names such as freeloader, user, parasite to those that do not follow the rule of giving back after receiving.

When someone remembers your birthday, you feel a future obligation to remember theirs. Receive a personalised holiday season greeting card in the mail and we feel the need to send one in return. Get a free sample of a product and you are more likely to purchase that product – in one study, shoppers at a candy store were 42 percent more likely to make a purchase if they received a gift piece of chocolate upon entry to the store.

The rule of reciprocation is pervasive across all human cultures and according to cultural anthropologists these feelings of future obligation made an enormous difference to human evolution as it allowed a person to give something (such as food, energy, care) to another with confidence that it would not be lost.

THE RESULTS

After collecting 634 instances of towel reuse the results are shown in the chart below.

Interestingly, those that saw the second message offering to donate to a nonprofit environmental protection organisation if they reused their towels (30.7 percent) were slightly less likely to participate that those that received the standard message (35.1 percent).

Those that received the third message however were significantly more likely to participate and reuse their towels (45.2 percent). The researchers concluded that this result was “due to an enhanced sense of obligation to reciprocate the hotel’s actions” – the rule of reciprocation in its full glory.

WHAT THIS MEANS FOR SUSTAINABILITY PROFESSIONALS

As sustainability professionals, we are constantly trying to influence or persuade people to participate in our sustainability initiatives, change their behaviour, volunteer their time, buy our product or service, or approve our project budget.

Behavioural science offers a vast array of influence and persuasion tools that sustainability professionals can employ to deliver more positive impacts from their efforts. There are two key lessons from the towel reuse study:

Use incentives with care. Mixing incentives is a bit like chemistry – put the wrong elements together and you can end up with an undesirable outcome. The rule of reciprocation is a powerful force. What can you give someone that is meaningful and unexpected that they will appreciate? Our free guide on the 3 key problems people are trying to solve is a great place to get ideas for this.

With great power comes great responsibility so use this new knowledge with care.