The question of whether cash aid helps or hurts children is central to social policy. Progressives argue that poor children need an income floor, citing research that shows even brief periods of childhood poverty can lead to lower adult earnings and worse health. Conservatives say unconditional payments erode work and marriage, increasing poverty in the long run.

President Bill Clinton changed the Democratic Party’s stance a quarter-century ago by abolishing welfare guarantees and shifting aid toward parents who work. Though child poverty subsequently fell to record lows, the reasons are in dispute, and rising inequality and volatility have revived Democratic support for subsidies.

There are a variety of public and private programs underway in the United States to measure the effects of a guaranteed income on poor families, and many other rich countries offer broad children’s allowances without condition.

The temporary expansion of the child tax credit, passed last year, offered subsidies to all but the richest parents at a one-year cost of more than $100 billion. Representative Suzan DelBene, Democrat of Washington, said the study strengthened the case for the aid by showing that “investing in our children has incredible long-term benefits.”

Greg J. Duncan, an economist at the University of California, Irvine, who was one of nine co-authors of the study, said he hoped the research would refocus the debate, which he said was “almost always about the risks that parents might work less or use the money frivolously” toward the question of “whether the payments are good for kids.”

But a conservative welfare critic, Robert Rector of the Heritage Foundation, argued that the study vindicated stringent welfare laws, which he credited with reducing child poverty by incentivizing parents to find and keep jobs.

“If you actually believe that child poverty has these negative effects, then you should not be trying to restore unconditional cash aid,” he said. “You certainly don’t want to go in the business of reversing welfare reform.”