New research from a World Bank-funded team in Lesotho, a tiny country in Southern Africa, investigated if they could reach individuals to persuade them to test for HIV. In Lesotho the rates of people with HIV are very high, as 40 percent of people between the ages 30 and 34 are HIV-positive.

The researchers recruited 3,427 volunteers in 29 villages. One group would come back every four months to be tested for two sexually transmitted infections that are curable. Volunteers were given small gifts to come back every four months.

Another group also came back for a test every four months, but these people didn't get a promise of a small stipend. They each got a lottery ticket. And there would be a drawing every four months. Two men and two women in each participating village would get a $50 prize, which is a lot of money in Lesotho. What the researchers found was extraordinary. After two years, there was a 21.4 percent reduction in HIV infections in the lottery ticket group compared with the volunteers who got the small gifts.

The researchers want to take this idea further and want to tell all the people who are participating for a lottery ticket that if they win, they get the cash only if they test negative for HIV.  The same psychological forces that cause people to believe they're going to win the lottery are now working to tell them, "I've got to practice safe sex."