Here is an experiment you don't want to try at home.

    Show a toy - a doll, say, or a model boat - to a toddler and explain that it it's something special you've had since you were little. Ask the child to be "very careful" with it. Hand over the toy, which appears to be in fine condition, except that you've secretly rigged it to break spectacularly as soon as the child handles it.

    When your precious toy falls apart, express regret by mildly saying, "Oh, my." Then sit still and observe the child.

    The point is not to permanently traumatize anyone - the researchers who performed this experiment quickly followed it with a ritual absolving the child of blame. But first, for 60 seconds after the toy broke, the psychologists recorded every reaction as the toddlers squirmed, avoided the experimenter's gaze, hunched their shoulders, hugged themselves and covered their faces with their hands.

    It was part of a long-term study at the University of Iowa to isolate the effects of two distinct mechanisms that help children become considerate, conscientious adults. One mechanism, measured in other experiments testing toddlers' ability to resist temptations, is called effortful self-control - how well you can think ahead and deliberately suppress impulsive behavior that hurts yourself and others.

    The other mechanism is less rational and is especially valuable for children and adults with poor self-control. It's the feeling measured in that broken-toy experiment: guilt, or what children diagnose as a "sinking feeling in the tummy."

    Guilt in its many varieties - Puritan, Catholic, Jewish, etc. - has often gotten a bad rap, but psychologists keep finding evidence of its usefulness. Too little guilt clearly has a downside - most obviously in sociopaths who feel no remorse, but also in kindergartners who smack other children and snatch their toys. Children typically start to feel guilt in their second year of life, says Grazyna Kochanska, who has been tracking children's development for two decades in her laboratory at the University of Iowa. Some children's temperament makes them prone to guilt, she said, and some become more guilt-prone thanks to parents and other early influences.

    "Children respond with acute and intense tension and negative emotions when they are tempted to misbehave, or even anticipate violating norms and rules," Dr. Kochanska said. "They remember, often subconsciously, how awful they have felt in the past."

    In Dr. Kochanska's latest studies, published in the August issue of The Journal of Personality and Social Psychology, she and colleagues found that 2-year-olds who showed more chagrin during the broken-toy experiment went on to have fewer behavioral problems over the next five years. That was true even for the ones who scored low on tests measuring their ability to focus on tasks and suppress strong desires to act impulsively.

    "If you have high guilt," Dr. Kochanska said, "it's such a rapid response system, and the sensation is so incredibly unpleasant, that effortful control doesn't much matter."

    But self-control was critical to children in the studies who were low in guilt, because they still behaved well if they had high self-control.

    "Even if you don't have that sinking feeling in the tummy, you can still suppress impulses," Dr. Kochanska said. "You can stop and remember what your parents told you. You can stop and reflect on the consequences for others and yourself."

    But what if your child lacks both self-control and guilt? What can you do? And should you feel guilty for doing a lousy job of parenting?

    Well, you could blame yourself, although researchers haven't been able to link any particular pattern of parenting to children's levels of guilt, says June Tangney, a psychologist at George Mason University. But Dr. Tangney, who has studied guilt extensively in both children and adults, including prison inmates, does have some advice for parents. （To offer your thoughts on parents and guilt, go to nytimes.com/tierneylab.）

    "The key element is the difference between shame and guilt," Dr. Tangney says. Shame, the feeling that you're a bad person because of bad behavior, has repeatedly been found to be unhealthy, she says, whereas guilty feelings focused on the behavior itself can be productive. But it's not enough, Dr. Tangney says, for parents just to follow the old admonition to criticize the sin, not the sinner. "Most young children," Dr. Tangney said, "really don't hear the distinction between 'Johnny, you did a bad thing' versus 'Johnny, you're a bad boy.' They hear 'bad kid.' I think a more active, directive approach is needed."

    She recommends focusing not just on the bad deed, but more important, on how to make amends. "Both children and adults can be surprisingly clueless about whether and how to make things right," Dr. Tangney said. "Little kids are overwhelmed by the spilled mess of milk on the floor. Parents can teach and support them to say 'I'm sorry' and to clean it up, maybe leaving the kitchen a little cleaner than it was before."

    That was the same atonement strategy, by the way, followed by the experimenters in Iowa who tricked the children with the broken toy. After the 60 seconds of angst, the children were asked what had happened and then were told that the toy could be easily repaired. The researcher would then leave the room with the broken toy and return in half a minute with an intact replica of it. The experimenter took the blame for having caused the damage, reassuring the children that it wasn't their fault and that the toy was now as good as new anyway.

    No harm, no foul, no guilt. If only the rest of their lives were so simple.

    這是一個你不愿試著在家里做的實驗。

    拿出一個玩具--一個娃娃亦或是一艘模型船。把它給一個剛學會走路的孩子，同時告訴他這個東西在你小時候對你有特別的意義。然后讓這個孩子要很好地愛護它。 把玩具交到他手中，除非是你在交接的一瞬間私下把它破壞得不成形，要不然，這個玩具就會完好無損。

    當珍惜的玩具被摔壞的時候，你的后悔也只是輕嘆一聲："噢，天啊。"然后仍然坐在原地看著孩子。

    關鍵是永遠不要去傷害別人。那些參與實驗的研究者們很快同意了這一觀點，以一種慣用于為孩子開脫責難的方式。但首先，在玩具被破壞的六十秒之后， 心理學家記錄下這些孩子扭動身體、避免與實驗者目光接觸、聳肩、蜷縮成一團并且用手捂著臉時的每個反映。

    這是愛荷華大學一項致力于分離由兩種不同方法對孩子產生的影響。這些方法能幫助孩子成為體貼的、盡職的成人。其中一種被應用于其他的測試孩子抗拒誘惑的能力的試驗中。這種方法被稱之為努力自我控制，也就是你如何很好地超前思考，并且從容不迫地抑制住這種會傷害你自己，也會傷害他人的沖動性行為。

    另一種方法相對欠缺合理性，但對于那些自我控制力差的孩子和大人特別有效。在那個被損壞了玩具的實驗中所體現的感情是負罪感或者說是孩子的一種內斂情緒（sinking feeling in the tummy）的表現。

    負罪感有很多種形式，比如：清教徒、天主教徒、猶太人等等。這種情感通常都會受到人們的責罵，但是心理學家一直致力于尋找負罪感有用的證據。只有很少的負罪感有著明顯的消極面。大部分的負罪感不僅明顯地存在于那些無負罪感的反社會者身上，而且也存在于那些打了其他孩子還搶他們玩具的幼兒園小朋友當中。在愛荷華大學實驗室已長達二十年之久的格羅蘇那。 Kochanska 認為，孩子會在兩歲的時候真正開始體驗什么是負罪感。她說："一些孩子的性格使得他們更容易有負罪感。 而且由于受到父母或其他的一些早期影響，有一些孩子更容易有負罪感傾向。"

    Kochanska博士說："當孩子被誘導做錯事的時候或者甚至違反預期的行為準則時，孩子會有強烈的緊張感和消極情緒。他們會經常下意識地記住他們過去時多么的糟糕。"

    Kochanska博士八月份出版在人格與社會心理學雜志中的最新研究中，她和她的同事發現那些在破損哇玩具實驗中顯得比較較為懊惱的兩歲大的孩子在其后超過五年的時間里不太會出現行為上的問題。這同樣體現在那些在評估他們注意力和抑制沖動能力的測試中得分較低的孩子身上。

    "如果一個人有強烈的負罪感，身體作為一個快速反應的系統，會讓你感覺極度不舒服。而自身的控制是不會起很大作用的。"Kochanska博士說道。但是自我控制對那些在學習中負罪感不強的孩子來說是非常重要的。因為假使有很強的自控力，他們就會一直有良好的行為。

    Kochanska博士認為，即使你沒有那種內在的感受，你仍可以繼續抑制沖動。你可以停下來去想想父母告訴過你的話。你可以可以停下來反思一下對于他人和自己所產生的結果。

    但是如果你的孩子既缺乏自控能力有缺乏負罪感，那么你該怎么辦？你該為自己糟糕的養育工作而感到有負罪感嗎？

    瓊。坦尼，喬治梅森大學的心理學家，說："那么，雖然研究者不能把任何一種特定的教育方式和孩子的負罪感聯系起來，不過你可能要責備你自己了。"但是，致力于研究兒童與成人，包括那些囚犯負罪感的坦尼教授還是給了父母們一些建議。（要發表你對父母和負罪感的想法，請登錄nytimes.com/tierneylab）

    坦尼教授說："關鍵因素是羞恥感和負罪感的差別。羞恥感是一種因為你做了壞事而感到覺得自己是個壞人。"她認為這種感覺已多次被發現是不健康的，然而被關注的負罪感行為本身是有益的。坦尼博士認為對于父母來說，僅僅是依靠老的訓誡來批評罪行而不是有罪過的人是不夠的。"大部分的小孩子是聽不明白 '喬尼，你做了壞事'和'喬尼，你是個壞孩子'之間的差別的。他們聽到的只有'壞孩子'.我認為我們需要一種更積極，更直接的方法。"坦尼博士這樣說。

    她建議不要把重點放在壞事情上，而更重要的是，要關注如何補救。坦尼博士說："孩子和大人呢都極有可能對是否該和如何做對事情一無所知。牛奶打翻在地會使小孩子不知所措。父母這時要教并鼓勵他們說'對不起',然后再把地板打掃干凈，或許這能讓廚房比之前更干凈。"

    這同樣是一種補償戰術。順便提一句，這種戰術是由來自愛荷華大學的那些用破損玩具逗小孩兒的實驗者所提出來的。在六十秒的焦慮之后，孩子們被問到發生了什么事情，然后被告知這些玩具很容易被修好。研究者們隨后帶著破損的玩具離開了房間，半分鐘后拿著完好無損的復制品回到了房間。實驗者承擔起弄壞玩具的責任，讓孩子重新確認這不是他們的過錯，并且讓他們明白現在玩具和新的是一樣的。

    沒有傷害，沒有犯規，沒有罪惡。要是孩子們的余生是如此簡單就好了。