When I was in training overseas in the Peace Corps, I came down with a very unpleasant digestive infection because I'd drunk unboiled water. I was not alone. While all the trainees knew we were supposed to take this extra step, others got caught out too. The problem was the social consequences: Even though the local families we lived with were wonderful and would have accommodated us, they themselves did not always boil the water before drinking it. After a while, it simply became hard to ask. (Not after we got sick, though! Consequences . . .)
Decades ago, rural folk in a particular South American village typically did not boil their water, and a number were periodically coming down with infections as a result. All of the local water sources were contaminated. For these low-income people, the extra effort and fuel involved in boiling was one barrier, but not insuperable. So this seemed on the surface a great opportunity for public health officials to offer assistance, and a local health worker tried to convince the villagers to change. Doable, right?
The villagers' lack of scientific knowledge was one of the challenges. The existence of invisible microbes was news to them, and let's face it, the idea that living things far too small to see can make you sick is not an obvious one. It took many years until this fact was demonstrated and accepted in Western science. But the upshot was that traditional village rules about when water should and should not be boiled amounted to longstanding albeit unscientific taboos. The delays between drinking contaminated water and getting sick did not help, given all the other possible sources of sickness, and of course people frequently drank the water without becoming ill. The consequences simply were not clear.
Of about 200 families in the village, special efforts were made with 21. Of these, 11 did start boiling regularly--but that was after two years of effort. How very frustrating, and how sad to think of the unnecessary suffering.
Modeling can have very large effects on behavior and consequence value: Getting respected village leaders on your side means a huge advantage in supporting change. But that's easier said than done. Rogers analyzed why a few of the villagers did switch: One woman was already a social outsider, so she had little to lose from the disapproval of others. Another adopter was a social insider more subject to peer pressure, but her medical conditions made it traditionally acceptable for her to boil.
More broadly, of course the power of community social norms and traditional knowledge was and is significant. So how best to disseminate evidence-based "best practice"--and make changes like boiling water sufficiently reinforcing? We're still working on that, but we've made significant progress. Certainly the importance of treating contaminated water is noncontroversial now in most places in the world. Change seldom comes overnight, and it takes work. Knowing something about the science of consequences can help.