摘要：Objectives. We pretested interventions derived from different domains of behavior change theory to determine their effectiveness at increasing hand washing with soap in a natural setting. Methods . We installed wireless devices in highway service station restrooms to record entry and soap use. Two text-only messages for each of 7 psychological domains were compared for their effect on soap-use rates. We collected data on nearly 200 000 restroom uses. Results . The knowledge activation domain was most effective for women, with a relative increase in soap use of 9.4% compared with the control condition ( P = .001). For men, disgust was the most effective, increasing soap use by 9.8% ( P = .001). Disgust was not significantly better than the control condition for women, nor was knowledge activation for men. Messages based on social norms and social status were effective for both genders. Conclusions . Our data show that unobtrusive observation of behavior in a natural setting can help identify the most effective interventions for changing behaviors of public health importance. The gender differences we found suggest that public health interventions should target men and women differently. Health promotion is expensive, with large sums invested worldwide in trying to change people's behavior. Yet many behavior-change campaigns prove to be largely ineffective, such as those targeting binge drinking, 1 diet, 2 , 3 adolescent sexual practices, 4 , 5 or washing hands with soap. 6 , 7 It would be helpful if the components of a behavior-change campaign were pretested for effectiveness before rolling out the campaign at scale. 8 Despite the potential advantages of early pretesting, relatively few public health interventions have employed this tactic. Hand washing with soap (hereafter referred to as “hand washing”) has been ranked the most cost-effective intervention for the worldwide control of disease. 9 , 10 It could save more than a million lives a year from diarrheal diseases 11 and prevent respiratory infections, 12 the 2 biggest causes of child mortality in developing countries. In developed countries, hand washing is important in preventing the spread of viral infections, including norovirus, 13 rotavirus, 14 and influenza 15 , 16 ; it also prevents the spread of hospital-acquired infections such as methicillin-resistant Staphylococcus aureus and Clostridium difficile . 17 A recent study that we conducted in the United Kingdom showed that a quarter of commuters sampled had fecal bacteria on their hands. 18 However, we still do not know the most effective way of encouraging hand washing. A common problem with studies of behavior is that self-reporting can be unreliable. Hand washing, like many health-related behaviors, is socially desirable and morally laden and hence tends to be vastly overreported in interviews. 19 , 20 An alternative to self-reporting is direct observation. However, methods such as structured observation of hand washing can also provide biased estimates of real behavior because being watched can affect hand-washing practice. 21 Unobtrusive monitoring of hand-washing behavior could provide an unbiased estimate of natural behavior as well as a means of measuring the efficacy of different interventions. Advocates argue that theory-based interventions have been shown to be more effective than other interventions. 22 , 23 However, there are many theories to choose from, each with several component domains and each capable of being instantiated in many forms. The epidemiological gold standard for testing interventions, the randomized controlled trial, can only compare a few interventions against a control. Comparing interventions simultaneously is a cost-effective means of maximizing the effects of a program and of avoiding expensive mistakes in large-scale programs. It could also be used in theory development, because the performance of interventions derived from different theoretical domains can be compared. For this study, we pretested the effects of messages targeting a range of theoretical domains important to behavior change by comparing many different interventions simultaneously to determine which were the most effective. 8 Previous work consolidated the many theoretical constructs within psychological theories of behavior into types of domains, such as knowledge, behavioral regulation, and motivation, for practical use in designing health interventions. 24 This work provided a theoretical foundation for our study, supplemented by a review of empirical knowledge from formative research studies about the motivations for hand washing, which showed that the determinants of hand washing include disgust, comfort, affiliation (or social norms, the desire to conform with what others do or with what appears to be socially acceptable behavior), and habit. 25 , 26 Disgust 27 and social norms 28 , 29 (elicited by the visible presence of other people in public restrooms) have been shown to increase hand washing in other studies. Although health education is a common strategy, it has been shown to be ineffective at changing hygiene behaviors. 30 , 31 One recent study showed that interventions relying on disgust were more effective than educational messages at increasing hand washing. 32
