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.

    这是一个你不愿试着在家里做的实验。

    拿出一个玩具--一个娃娃亦或是一艘模型船。把它给一个刚学会走路的孩子，同时告诉他这个东西在你小时候对你有特别的意义。然后让这个孩子要很好地爱护它。 把玩具交到他手中，除非是你在交接的一瞬间私下把它破坏得不成形，要不然，这个玩具就会完好无损。

    当珍惜的玩具被摔坏的时候，你的后悔也只是轻叹一声："噢，天啊。"然后仍然坐在原地看着孩子。

    关键是永远不要去伤害别人。那些参与实验的研究者们很快同意了这一观点，以一种惯用于为孩子开脱责难的方式。但首先，在玩具被破坏的六十秒之后， 心理学家记录下这些孩子扭动身体、避免与实验者目光接触、耸肩、蜷缩成一团并且用手捂着脸时的每个反映。

    这是爱荷华大学一项致力于分离由两种不同方法对孩子产生的影响。这些方法能帮助孩子成为体贴的、尽职的成人。其中一种被应用于其他的测试孩子抗拒诱惑的能力的试验中。这种方法被称之为努力自我控制，也就是你如何很好地超前思考，并且从容不迫地抑制住这种会伤害你自己，也会伤害他人的冲动性行为。

    另一种方法相对欠缺合理性，但对于那些自我控制力差的孩子和大人特别有效。在那个被损坏了玩具的实验中所体现的感情是负罪感或者说是孩子的一种内敛情绪（sinking feeling in the tummy）的表现。

    负罪感有很多种形式，比如：清教徒、天主教徒、犹太人等等。这种情感通常都会受到人们的责骂，但是心理学家一直致力于寻找负罪感有用的证据。只有很少的负罪感有着明显的消极面。大部分的负罪感不仅明显地存在于那些无负罪感的反社会者身上，而且也存在于那些打了其他孩子还抢他们玩具的幼儿园小朋友当中。在爱荷华大学实验室已长达二十年之久的格罗苏那。 Kochanska 认为，孩子会在两岁的时候真正开始体验什么是负罪感。她说："一些孩子的性格使得他们更容易有负罪感。 而且由于受到父母或其他的一些早期影响，有一些孩子更容易有负罪感倾向。"

    Kochanska博士说："当孩子被诱导做错事的时候或者甚至违反预期的行为准则时，孩子会有强烈的紧张感和消极情绪。他们会经常下意识地记住他们过去时多么的糟糕。"

    Kochanska博士八月份出版在人格与社会心理学杂志中的最新研究中，她和她的同事发现那些在破损哇玩具实验中显得比较较为懊恼的两岁大的孩子在其后超过五年的时间里不太会出现行为上的问题。这同样体现在那些在评估他们注意力和抑制冲动能力的测试中得分较低的孩子身上。

    "如果一个人有强烈的负罪感，身体作为一个快速反应的系统，会让你感觉极度不舒服。而自身的控制是不会起很大作用的。"Kochanska博士说道。但是自我控制对那些在学习中负罪感不强的孩子来说是非常重要的。因为假使有很强的自控力，他们就会一直有良好的行为。

    Kochanska博士认为，即使你没有那种内在的感受，你仍可以继续抑制冲动。你可以停下来去想想父母告诉过你的话。你可以可以停下来反思一下对于他人和自己所产生的结果。

    但是如果你的孩子既缺乏自控能力有缺乏负罪感，那么你该怎么办？你该为自己糟糕的养育工作而感到有负罪感吗？

    琼。坦尼，乔治梅森大学的心理学家，说："那么，虽然研究者不能把任何一种特定的教育方式和孩子的负罪感联系起来，不过你可能要责备你自己了。"但是，致力于研究儿童与成人，包括那些囚犯负罪感的坦尼教授还是给了父母们一些建议。（要发表你对父母和负罪感的想法，请登录nytimes.com/tierneylab）

    坦尼教授说："关键因素是羞耻感和负罪感的差别。羞耻感是一种因为你做了坏事而感到觉得自己是个坏人。"她认为这种感觉已多次被发现是不健康的，然而被关注的负罪感行为本身是有益的。坦尼博士认为对于父母来说，仅仅是依靠老的训诫来批评罪行而不是有罪过的人是不够的。"大部分的小孩子是听不明白 '乔尼，你做了坏事'和'乔尼，你是个坏孩子'之间的差别的。他们听到的只有'坏孩子'.我认为我们需要一种更积极，更直接的方法。"坦尼博士这样说。

    她建议不要把重点放在坏事情上，而更重要的是，要关注如何补救。坦尼博士说："孩子和大人呢都极有可能对是否该和如何做对事情一无所知。牛奶打翻在地会使小孩子不知所措。父母这时要教并鼓励他们说'对不起',然后再把地板打扫干净，或许这能让厨房比之前更干净。"

    这同样是一种补偿战术。顺便提一句，这种战术是由来自爱荷华大学的那些用破损玩具逗小孩儿的实验者所提出来的。在六十秒的焦虑之后，孩子们被问到发生了什么事情，然后被告知这些玩具很容易被修好。研究者们随后带着破损的玩具离开了房间，半分钟后拿着完好无损的复制品回到了房间。实验者承担起弄坏玩具的责任，让孩子重新确认这不是他们的过错，并且让他们明白现在玩具和新的是一样的。

    没有伤害，没有犯规，没有罪恶。要是孩子们的余生是如此简单就好了。