He says they add humor and a sense of activity.

VOA: special.2009.09.09

Walking is something you can do with others, in the sense that it can be a joint activity,a joint undertaking.

走路是一件你能和他人一起做的事，这是一个共同合作的行为和事件。

耶鲁公开课 - 死亡课程节选

Walking is something you can do with others, in the sense that it can be a joint activity,a joint undertaking.

走路是一件你能和他人一起做的事，这是一个共同合作的行为和事件。

耶鲁公开课 - 死亡课程节选