孩子经常会争夺父母的爱，但有些争夺不来，因父母偏心有科学证据。研究发现，父母往往更偏爱女儿，个性随和、认真的孩子也更惹人爱。

But just like looking at the rings can show events in the life of a tree, researchers from Brigham Young University have found that testing only a few strands of a person's hair can reveal ...