Wolfram Schultz recorded dopamine neurons in monkeys receiving juice. At first, they fired when the juice arrived. Once a light signaled it, they fired at the light, not the juice. And if promised juice never came, their activity dipped below normal. Dopamine tracks the gap between what you expect and what you get, which is why the unexpected is so gripping.
Remembering is not replaying a recording — it is rebuilding. Each time you recall a memory, it becomes temporarily malleable and can be altered before being stored again. That is why two people can sincerely remember the same event… differently.
In 2003, Johnson and Goldstein compared European countries. Where you must tick a box to become a donor, consent rates ranged from 4% to 28%. Where you're a donor by default unless you opt out, they topped 85%. People aren't more generous on one side; most simply stick with whatever option was chosen for them.