the.com/reciprocity
The invisible debt every favor secretly installs in someone else's conscience.
means The practice of exchanging things—favors, kindness, advantages—with others for mutual benefit, where one gesture is answered in kind.
from From Latin reciprocus, meaning 'moving backward and forward, returning the same way.' The word is thought to be built from re- ('back') and pro- ('forward'), capturing the image of a tide that goes out and comes back, or a motion that retraces its own path. English borrowed it through the 1500s as 'reciprocal,' with 'reciprocity' following close behind—naming the back-and-forth that ties two parties together.
hardwiredFree samples measurably boost sales through obligation, not taste
global glueEvery known human culture practices some form of gift-return
name originFrom Latin meaning back-and-forth, like a tide
dark sideBribes work by hijacking this exact instinct
animal versionVampire bats share blood with non-relatives who reciprocate