《老友记》里瑞秋说过这样一句话，"Once a cheater,always a cheater."最新研究表明，这种说法有科学依据。当一个人屡次欺骗伴侣时，大脑会逐渐适应并且压根不再对撒谎感到愧疚。

Admitting you were unfaithful in past relationships is a gamble. "Once a cheater, always a cheater" is a phrase that can damage your reputation for a long time, if you're unlucky.
承认你在之前的情侣关系中不忠是一次赌博。如果你不走运的话，“一日出轨，终身出轨” 这句短语则会长期损害你的声誉。

According to some scientific research, there could actually be some fact behind the idiom.
据一些科学研究，这个习语背后可能真的暗藏着某些事实。

A new study, published in the journal Archives of Sexual Behaviour, followed 484 participants in mixed gender romantic relationships. The researchers asked the participants to report their own "extra-dyadic sexual involvement" — having sexual relations with someone other than their partner — and also whether they had suspected their partners of infidelity in each romantic relationship they had been in.
近期，一项发表在《性行为档案》期刊的研究跟踪调查了484名参与者在男女婚恋关系中的情况。研究人员要求参与者上报他们的“劈腿”关系——与伴侣以外的人发生性关系——以及他们是否怀疑自己的伴侣在婚恋关系中不忠。

The results showed that people who had messed around in their first relationship were three times more likely to cheat in their next relationship compared to those who had stayed faithful.
结果表明，与那些对伴侣忠诚的人相比，那些在初恋就出轨的人在下一段感情中出轨的可能性要高出三倍。

Those who knew that their previous partners had cheated on them were twice as likely to have their next partners do the dirty on them too. Suspicion also appeared to be hard to shake, as people who suspected their first relationship partners of cheating were four times more likely to report suspicion in later relationships.
并且那些知道前任伴侣曾欺骗过自己的人，他们的下一任伴侣仍会出轨的可能性是其他人的两倍。猜忌是难以被消除的，因为那些怀疑自己第一任伴侣的人在接下来的感情中会有四倍的可能性怀疑伴侣仍会出轨。

One reason for this could be the fact that when we lie, our brain actually gets used to it. This was the finding of a study published in Nature Neuroscience, which showed that telling small lies desensitises our brains to the associated negative emotions, which may encourage us to tell bigger lies in the future.
其中一个原因可能就是，大脑能够习惯于撒谎。这项研究发表在《自然神经科学》杂志上，研究表明撒一些小谎会使我们的大脑对相关负面情绪产生麻木感，这可能会鼓励我们在未来撒下更大的谎言。

In other words, those little white lies we tell all the time might build up into bigger, more serious untruths.
换句话来说，我们一直撒下的那些善意的小谎也可能会累积成更大更严重的谎言。

In the study, participants were divided into pairs. One was shown a glass jar full of coins, and the other a blurry picture of the same jar. The participant with the jar was instructed to help their partner guess how many coins it contained.
在研究中，参与者被分成两两一组。研究人员向其中一位参与者出示了一个装满硬币的玻璃罐，向另一位出示了同一个罐子的模糊图像。拥有罐子的参与者被告知要帮助他们的搭档猜出里面装了多少硬币。

One group of participants were told they would get a cash prize if their partner overestimated the number of coins, leading them to lie and exaggerate. The researchers saw that the amygdala — the area of the brain responsible for emotions — responded when participants lied, but this response weakened when lies were repeatedly told.
其中一组参与者被告知，如果他们的搭档高估了硬币的数量，他们就会得到现金奖励，这导致他们会尽力撒谎和夸大事实。研究人员发现当参与者说谎的时候，大脑中负责处理情感的杏仁核会做出反应，但当参与者经常说谎时，杏仁核的反应会减弱。

A similar thing could happen when somebody cheats on their partner. The first time they do it, they will probably feel terrible. However, if it happens again, they will feel slightly less bad, and so on. It could all be down to the biology of the brain, and what the amygdala is making you feel.
当一些人欺骗他们的伴侣时，也会发生类似的事情。当他们第一次对伴侣撒谎时，他们会感到难受。然而，如若再次撒谎，他们就不会感觉那么糟等等。这一切都取决于大脑的生物学，以及杏仁核让你感受到的东西。

In an interview with Elite Daily, researcher at Princeton Neuroscience and co-author of the study Neil Garrett said: "What our study and others suggest is a powerful factor that prevents us from cheating is our emotional reaction to it, how bad we feel essentially, and the process of adaptation reduces this reaction, thereby allowing us to cheat more."
在接受《精英日报》采访时，普林斯顿神经科学系的研究员和研究合著者尼尔•加勒特说：“我们的研究和其他研究表明，阻止我们欺骗他人的一个重要因素就是我们对欺骗的情绪反应，我们会感觉到有多糟糕，而适应欺骗的这个过程减少了情绪反应，从而使我们能够再次撒谎。”

"With serial cheaters, it could be the case that they initially felt bad about cheating, but have cheated so much they've adapted to their ways and simply don't feel bad about cheating any more."
“对于一些经常撒谎的人，起初他们可能会觉得欺骗他人的感觉并不好受，但当他们多次撒谎后，就已经适应了这种生活方式并且压根不再对撒谎感到愧疚。”

He added: "Another possibility is that they never felt bad about cheating to begin with, so they didn't need adaptation to occur, they were comfortable with it from the get-go."
他补充道：“另一个可能性就是从一开始他们就对欺骗他人没有什么感觉，所以他们不需要适应，他们从一开始就感到十分自在。”