The study, published in the October issue of the Journal of Consumer Research, found that the types of signs posted in hotel bathrooms had different effects -- signs that focused on the environmental benefits were less effective than signs that pointed out the level of participation of other guests.

Study authors Noah J. Goldstein of the University of Chicago, Robert B. Cialdini and Vladas Griskevicius, both Arizona State University, got a hotel chain to allow them to create a series of different towel re-use cards, which were placed in the hotel's bathrooms.

Some cards read "Help Save the Environment" and others read "Join Your Fellow Guests in Helping to Save the Environment."

Cards that focused on the level of participation of other guests, increased the percentage of participation from 35.1 percent to 44.1 percent.

In a second study, the researchers were able to boost towel reuse even further by placing a sign in the room that said 75 percent of guests in that specific room re-used their towels.