Panksepp has studied rats and found that when they play, they often chirp—a primitive form of laughter, according to the scientist.

潘克塞普曾对老鼠进行了相关研究，他发现，当老鼠玩耍的时候，他们经常发出一种唧唧喳喳很尖的声音——根据科学家表示，这是笑的一种原始形态。