The struggle for insufficient resources—time, money, food, companionship—concentrates the mind for better and, mostly, worse, according to this revelatory treatise on the psychology of scarcity. Harvard economist Mullainathan and Princeton psychologist Shafir examine how scarcity in many forms, from poverty and scheduling pressures to dieters' food cravings and loneliness—a kind of "social scarcity"—force the brain to focus on alleviating pressing shortages and thus reduce the mental "bandwidth" available to address other needs, plan ahead, exert self-control, and solve problems. The result of perpetual scarcity, they contend, is a life fixated on agonizing trade-offs, crises, and preoccupations that impose persistent cognitive deficits—in poor people they lower mental performance as much as going a night without sleep—and reinforce self-defeating actions. The authors support their lucid, accessible argument with a raft of intriguing research in psychology and behavioral economics (sample study: "We recruited Princeton undergraduates to play Family Feud in a controlled setting") and apply it to surprising nudges that remedy everything from hospital overcrowding to financial ignorance. Mullainaithan and Shafir present an insightful, humane alternative to character-based accounts of dysfunctional behavior, one that shifts the spotlight from personal failings to the involuntary psychic disabilities that chronic scarcity inflicts on everyone. 8 illus. Agent: Katinka Matson, Brockman Inc. (Sept.)