Clean Water

SODIS is a simple method for disinfecting water in areas where lots of kids get sick and die from bad water.  Basically, you pour water into plastic bottles, put 'em on your roof for a day or two, and the water is clean.  But Katja Grace points us to a study showing that it's surprisingly hard to get people to do this:

The technical barrier is that people don’t do it much. About thirty two percent of participants in the study used the system on a given day....The leader of the study, Daniel Mausezahl, suspects a big reason for this is that lining up water bottles on your roof shows your neighbors that you aren’t rich enough to have more expensive methods of disinfecting water.

....Fascinating as signaling explanations are, this seems incredible. Having live descendents is even more evolutionarily handy than impressing associates. What other explanations could there be? Perhaps adults are skeptical about effectiveness?....Parents are known for obsessive interest in their children’s safety. What’s going on?

Skepticism sounds like a reasonable guess.  Or maybe parents know that their kids drink water from lots of different places, so cleaning up their own supply doesn't seem very effective unless everyone else is doing it too.  Or maybe it just takes a while for cultural norms to change.