But here’s what Cialdini found: the return favor is often dramatically larger than the original one. A 50-cent sample can trigger a €50 purchase. A free coffee might land a million-dollar contract. Is this manipulation? Maybe. But it's also deeply human.

The Zeigarnik Effect is actually quite simple: Your brain holds onto unfinished tasks. Kinda like a dog with a bone, if it’s not chewed up, it’s coming along.
Think about it: 

• The dirty dishes in the sink

• …