Freedom from financial stress allows mothers to spend more time bonding with their babies would be the obvious hypothesis. Money definitely gives the poor more freedom to control their own lives.

Cash directly causes a lot of benefits to children that could improve cognitive function.

Among them:

- better (or more) food

- more time with parents

- better medical care

- better housing, which would reduce exposure to things like lead

So no, it's not like a baby sits next to a stack of cash and gets healthier, obviously. But it's very easy to understand why richer children are healthier and function better.

You've reminded me of the Southpark with Magic Johnson where they discover large amounts of cash is the literal cure for AIDS.

Money solves or allieviates many, many problems, actually.

Stress, lack of sleep, and poor nutrition among them.

malnutrition would be an obvious cause.