Their inability to scowl seemed to impair their ability to see why pushy telemarketers or a lack of birthday wishes might make one's face fall.

他们无法动怒似乎削弱了他们的能力，让他们明白为什么咄咄逼人的电话推销员或没得到生日祝愿可能会让一个人沉下脸来。