3. 眼角沒有皺紋的笑容可能是假笑

If someone's trying to look happy but really isn't, you won't see the wrinkles.
如果有人試圖表現出開心的樣子，但并不是發自內心的高興，那么你是看不見對方的笑紋的。

More recently, a study from Northeastern University researchers found that people could do a pretty good job of faking a Duchenne smile, even when they weren't feeling especially happy.
最近，美國東北大學的一項研究發現，人們即使并沒有感到特別開心，也能偽裝出完美的假笑。

It seems safe to say that if the crinkles aren't there, the person's probably not genuinely happy. But just because the crinkles are there doesn't necessarily mean they're elated.
所以比較保險的說法是，沒有皺紋的笑容證明一個人可能不是真正的快樂。但僅僅因為笑出皺紋，也不能確定一個人真的很開心。