They had 2 messages for the hotel guests. A standard one focused on environmental protection "HELP SAVE THE ENVIRONMENT. You can show your respect for nature and help save the environment by reusing your towels during your stay." The other message had a descriptive norm informing people that a majority of other guests reused their towels: “JOIN YOUR FELLOW GUESTS IN HELPING TO SAVE THE ENVIRONMENT. Almost 75% of guests who are asked to participate in our new resource savings program do help by using their towels more than once. You can join your fellow guests in this program to help save the environment by reusing your towels during your stay."
The messages were randomly assigned to different hotel rooms. Towel reuse went up from about 30% in the standard message to 44% with the descriptive norm message. With further adjustment to the wording “JOIN YOUR FELLOW GUESTS IN HELPING TO SAVE THE ENVIRONMENT. In a study conducted in Fall 2003, 75% of the guests who stayed in this room participated in our new resource savings program by using their towels more than once. You can join your fellow guests in this program to help save the environment by reusing your towels during your stay", they increase towel reuse to 50%.
Descriptive norms improve towel reuse at least in hotel bathrooms but does this work in other areas. The Behavioural Insights Team, the so called Nudge Unit of the Cabinet Office, looked at charitable donations in wills. The average donation was £3,300. When people rang to book a will-writing appointment they were randomly assigned to one of two groups of will-writers. The first took their details and then asked "Would you like to leave any money to charity in your will?". The second said "many of our customers like to leave money to charity in their will. Are there any causes you’re passionate about?” The first or "Plain Ask" method had no effect on donations but the second social normative doubled the average donation to £6,661.
The results are important for hoteliers and charities but also have implications for doctors and nurses trying to improve the uptake of health promotion programs. If we can introduce social norms into our recommendations this is likely to improve the chance that our advice is followed.