Picture an apple. For most people, an image appears, sharp or hazy. For others, nothing: they know what an apple looks like but don't “see” it. Francis Galton noticed these differences as early as 1880; in 2015, neurologist Adam Zeman gave them a name, aphantasia. Depending on the study, roughly 1% to 4% of people have it, often without realizing that others literally see pictures in their heads.
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.