We find that people imitate not only the particulars of positive actions, but also the spirit underlying them. This implies that kindness itself is contagious, and that it can cascade across people, taking on new forms along the way.
We still don’t fully understand the psychological forces that power kindness contagion. One possibility, supported by our own work, is that people value being on the same page with others. For instance, we’ve found that when individuals learn that their own opinions match those of a group, they engage brain regions associated with the experience of reward, and that this brain activity tracks their later efforts to line up with a group. As such, when people learn that others act kindly, they might come to value kindness more themselves.
– Jamil Zaki