Former Brazilian President Luiz Inácio Lula da Silva speaks on the 10th anniversary of Bolsa Familia, in 2013.

SÃO PAULO—Brazil, as you might have heard from dozens of think pieces, has a “rising middle class.” And one of the factors credited with pulling millions of Brazilians out of poverty is Bolsa Família, a 10-year-old, conditional cash-transfer program that rewards families for sending their kids to school and taking them to regular health check-ups.

Bolsa’s terms, by American standards, are pretty radical: Every month, 50 million poor parents, or a quarter of the country’s population, get a handout equal to about $35 to $70, plus more for additional children.

And I do mean “handout.” They don’t pay it back. It doesn’t run out. Recipients don’t have to prove they’re looking for work.

“It's like Sweden with sunshine,” is how one economist described the arrangement.

But there’s another reason Bolsa is unusual: Though “Bolsa Família” translates to “family grant,” it’s doled out primarily to the woman of the house.

“The state tends to believe women are more reliable than men,” said Sérgio Fausto, a political scientist and executive director of the Instituto Fernando Henrique Cardoso think tank in São Paulo.

The thinking here, like in other countries that offer cash transfers and microloans primarily to women, is that mothers are more likely to use the money to help their children, while men might squander the cash or skip town with it. This is especially a concern in parts of Brazil where widespread alcoholism is both a driver and outcome of grinding poverty.