The psychologist alone can ask such questions: Why do we smile when pleased and not scowl?

只有心理学家才会问这样的问题：为什么我们高兴时微笑，而不是怒容满面？

youdao

When we smile to others, we can get a smile in return.

当我们对别人微笑时，我们可以得到一个微笑作为回报。

youdao

We smile to communicate a message.

我们笑是为了传达讯息。

youdao

"If we can bring some smile on people's faces - even if we don't do it exactly like it was done before - if they like it, that makes us happy."

VOA: standard.2010.05.28

So, he writes: To the psychologist alone can such questions occur as: Why do we smile when pleased and not scowl?

他这样写到：,对哲学家本身说,会出现这些问题：,为什么开心时我们微笑而非皱眉？

耶鲁公开课 - 心理学导论课程节选

The common man-- The common man can only say, "Of course we smile.

普通人，你们中没有普通人-,普通人只会说，当然，我们微笑。

耶鲁公开课 - 心理学导论课程节选

"We smile because we feel not threatened, " says Dr. Pressman.

WSJ: Stress-Busting Smiles

Cage gazes at Fonda with his characteristic look of stricken canine ardor, Fonda flashes back one of her radiantly loopy grins, and we smile at both the rightness and the weirdness of their union.

NEWYORKER: It Could Happen to You

Because smiling is evolutionarily contagious and we have a subconscious innate drive to smile when we see one.

FORBES: The Untapped Power Of Smiling