In 2018, researcher Jeffrey Hall surveyed adults who had recently moved and first-year college students about their new relationships. By his estimates, it takes about 50 hours together to go from acquaintance to casual friend, 90 hours to become friends, and more than 200 hours to become close friends. Time spent working side by side counts for little: it's leisure time, chatting and joking, that makes the difference.
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.