Robert Cialdini, then a professor of marketing and psychology at Arizona State University, and his colleagues conducted a series of experiments to explore how hotels could get more visitors to reuse their towels, thereby conserving resources (and boosting a hotel’s bottom line). But the researchers wondered whether learning that lots of other people reused their towels would prove even more motivational. To find out, they had the hotel leave the usual sign on the washroom towel racks of one group of rooms — the sign emphasized that reusing towels was environmentally friendly — and gave another group of rooms signs with the additional information that “almost 75% of guests who are asked to participate in our new resource savings program do help.” This second group turned out to be more than 25 percent more likely to reuse their towels. 