這貌似是一個奇怪的反應：當你高興的時候會流淚。不過，一些心理學家稱，他們發現了其中的原因，喜極而泣很有可能是身體恢復“情感平衡”的方式。

這些心理學家稱，通過消極情緒對勢不可擋的積極情緒做出回應，人們能夠從強烈的情緒中更好地恢復過來。

耶魯大學的心理學家測試受試者對不同場景的情緒反應，包括歡聚和面對可愛孩子的場景。他們發現，用消極反應表達積極消息的人能夠更快地緩和其強烈的情感，在孩子畢業典禮上最可能哭的人最可能想捏一個可愛的孩子的臉頰。

他們引用了人們用消極情緒回應積極經歷的其他例子，包括樂迷在他們的偶像出現時驚恐地尖叫和彩票贏家喜極而泣。

心理學家還表示，有一些證據表明強烈的消極情感也可能引起積極的表情。例如，當人們緊張或者面對困難或可怕的境遇時，他們經常會大笑。

It may seem like a strange response: to break down in tears when you are happy.

But now a group of psychologists say they have found the reason why, and that crying tears of joy may well be the body’s way of restoring “emotional equilibrium”.

The psychologists say that, by responding to an overwhelmingly positive emotion with a negative one, people are able to recover better from strong emotions.

Oriana Aragon, the lead author of the report which will be published in the journal Psychological Science,said: “People may be restoring emotional equilibrium with these expressions.

“They seem to take place when people are overwhelmed with strong positive emotions, and people who do this seem to recover better from those strong emotions.”

The psychologists from Yale University examined subjects’ emotional responses to different scenarios, including happy reunions and “cute” babies.

They found individuals who expressed negative reactions to positive news were able to moderate their intense emotions more quickly.

They also found people who are most likely to cry at their child’s graduation are also most likely to want to pinch a cute baby’s cheeks.

They cited other examples of where people responded to a positive experience with a negative emotion, including concert goers screaming in horror at the presence of their idol and lottery winners breaking down in tears.

The report authors said: "To give an example, upon winning the lottery, one might appraise the event as an incredibly good thing; feel overwhelmed with happiness, smile and cry.

"One’s appraisal that winning is a good thing, intense happiness and verbal expression would easily be described as positive, yet there is also an expression of crying which normatively expresses sadness.

"This expression is not inherent to the situation, the appraisal, or the positive emotions. The negative expression might be merely a facial display, or it might reflect actual negative emotions."

Miss Aragon said: "I was surprised no one ever asked why that is."

Miss Aragon, a postdoctoral associate at Yale, said the research went some of the way to explaining a common response that most people did not understand.

“These insights advance our understanding of how people express and control their emotions, which is importantly related to mental and physical health, the quality of relationships with others, and even how well people work together,” she said.

The psychologists claimed that there was also some evidence that the reverse was also true and that strong negative feelings may provoke positive expressions.

For example, people often laugh when they are nervous or confronted with a difficult or frightening situations. They cite previous studies where psychologists found some subjects smiled at times of extreme sadness.

The study called Dimorphous Expressions of Positive Emotion: Displays of Both Care and Aggression in Response to Cute Stimuli, will be published this month.

（來源：Daily Telegraph 編輯：祝興媛）