He signed the e-mail, “I am bitterly, bitterly disappointed. Dad.”

That e-mail, released by one of his daughters hoping to get publicity for a book she is translating, has made Crews a hugely popular folk hero in Britain. Many parents are apparently delighted that someone finally had the gumption to give at least one set of overprivileged slackers a well-deserved kick in the pants.

The problem, of course, is that no matter how emotionally satisfying these tirades may be, they don’t really work. You can tell people that they are fat and that they shouldn’t eat more French fries, but that doesn’t mean they will stop. You can make all sorts of New Year’s resolutions, earnestly deciding to behave better, but that doesn’t mean you will.

People don’t behave badly because they lack information about their shortcomings. They behave badly because they’ve fallen into patterns of destructive behavior from which they’re unable to escape.

Human behavior flows from hidden springs and calls for constant and crafty prodding more than blunt hectoring. The way to get someone out of a negative cascade is not with a ferocious e-mail trying to attack their bad behavior. It’s to go on offense and try to maximize some alternative good behavior. There’s a trove of research suggesting that it’s best to tackle negative behaviors obliquely, by redirecting attention toward different, positive ones.

It’s foolish to imperiously withdraw and say, come back to me when you have a plan. It’s better to pick one area of life at a time (most people don’t have the willpower to change their whole lives all at once) and help a person lay down a pre-emptive set of concrete rules and rewards. Pick out a small goal and lay out measurable steps toward it.

It’s foolhardy to try to persuade people to see the profound errors of their ways in the hope that mental change will lead to behavioral change. Instead, try to change superficial behavior first and hope that, if they act differently, they’ll eventually think differently. Lure people toward success with the promise of admiration instead of trying to punish failure with criticism. Positive rewards are more powerful.