"A few years ago, Cialdini, a professor at Arizona State University, conducted a study in several Phoenix hotels comparing the effects of those ubiquitous hotel-bathroom placards that ask guests to reuse towels, testing four slightly different messages. The first sign had the traditional message, asking guests to "do it for the environment." The second asked guests to "cooperate with the hotel" and "be our partner in this cause" (12 percent less effective than the first). The third stated that the majority of guests in the hotel reused towels at least once during their stay (18 percent more effective). The last message was even more specific: it said that the majority of guests "in this room" had reused their towels. It produced a 33 percent increase in response behavior over the traditional message."