In the checker-shadow illusion created by MIT's Edward Adelson in 1995, a light square in a cylinder's shadow and a dark square in full light are printed in the identical shade of gray. Your brain doesn't measure light; it corrects for shadows to guess objects' true colors. Even knowing the trick, you can't make them look the same.
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.