He once studied the effect of installing air bags in cars at a time when automakers were offering customers the option of buying cars with and without the safety devices. Winston found that people who bought cars with air bags tended to be the safest drivers to begin with. And now, lulled into a sense of security, they tended to drive faster, effectively canceling out the safety benefits.
Read the rest of Shankar Vedantam's article on well-intentioned interventions.
[HT: Arts & Letters Daily ]