If the teachers and the parents do not believe that the child can cross the hump and get into the steep part of the S—curve, they may as well not try: The teacher ignores the children who have fallen behind and the parent stops taking interest in their education. But this behavior creates a poverty trap even where none exists in the first place.

the parts of the brain corresponding to the limbic system (thought to respond only to more visceral, immediate rewards) were activated only when the decision involved comparing a reward today with one in the future. In contrast, the lateral prefrontal cortex (a more “calculating” part of the brain) responded with a similar intensity to all decisions, regardless of the timing of the options. Brains that work like this would produce a lot of failed good intentions. And indeed, we do see a lot of those, from New Year’s resolutions to gym memberships that lie unused.

The poor stay poor here because they do not save enough.

But then it is easy, too easy, to sermonize about the dangers of paternalism and the need to take responsibility for our own lives, from the comfort of our couch in our safe and sanitary home. Aren't we, those who live in the rich world, the constant beneficiaries of a paternalism now so thoroughly embedded into the system that we hardly notice it?

We must arm ourselves with patience and wisdom and listen to the poor what they want. This is the best way to avoid the trap of ignorance, ideology and inertia on our side.

If the rules make such a difference, then it becomes very important who gets to make them.