Scarcity: Why Having Too Little Means So Much by Sendhil Mullainathan and Eldar Shafir Times Books, 288 pp., $28.00

There is a great deal of unlovely jargon within the federal government. The product of an activity is called “the deliverable.” A task that follows a meeting is called a “do-out.” A request for action is described as “the ask.” If someone needs to continue a discussion with a colleague, he will promise to “circle back.” If a project must be abandoned or put on hold because of competing demands on people’s time and attention, the problem is one of “bandwidth.” Of course such terms can be found in many other places, including in businesses, but they are used with particular regularity in Washington, D.C.

Of the various unlovely terms, “bandwidth” is the most useful and the most interesting. The central idea is that public officials have the capacity to focus on, and to promote and implement, only a subset of the universe of good ideas. Bandwidth is limited partly for political reasons. In any particular period, members of Congress, executive branch officials, and the public itself may be unwilling to support more than a small set of proposals. But much of the problem involves the limits of time and attention. A proposed reform might seem excellent, and it might even be able to attract considerable political support, but the minds of the people who might pursue it are occupied, and they do not have the time to learn about it and to explore its merits. Within government, some good ideas fail to go anywhere, not because anyone opposes them, but because the system lacks the bandwidth to investigate them.

Economists focus on the problem of scarcity—on how people allocate their resources (including both time and money) in the face of many competing demands. In their extraordinarily illuminating book, the behavioral economist Sendhil Mullainathan and the cognitive psychologist Eldar Shafir explore something quite different, which is the feeling of scarcity, and the psychological and behavioral consequences of that feeling. They know that the feeling of scarcity differs across various kinds of experiences and that people can feel “poor” with respect to money, time, or relationships with others.

But their striking claim, based on careful empirical research, is that across all of those categories, the feeling of scarcity has quite similar effects. It puts people in a kind of cognitive tunnel, limiting what they are able to see. It depletes their self-control. It makes them more impulsive and sometimes a bit dumb. What we often consider a part of people’s basic character—an inability to learn, a propensity to anger or impatience—may well be a…