In synesthesia, one sense triggers another: a letter brings a color, a sound a shape, a word a taste. A large 2006 study estimated that around 4% of people have it. It isn't imagination: tested months apart, synesthetes match the same colors to the same letters with a consistency no one can fake.
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.