Roediger and Karpicke had one group read a text four times, and another read it once then test themselves three times. A week later, the self-testers recalled 61% versus 40% for the rereaders, who had felt more confident they'd learned it. Pulling information out of memory strengthens it far more than looking at it again.
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.