Rohrer and Taylor had students compute volumes of different solids. One group practiced each type in a block; the other got them shuffled. During practice, the blocked group looked better. But on a test a week later, the mixed group scored 63% versus 20%. Having to pick the right method each time is what makes it stick.
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.