There is an anecdote early in the book about a recruit the author knew in basic training. The other men would play pranks on him. The one I’m thinking of, they would ask him if he preferred a nickel or a dime (worth more in the 60s). He’d choose the nickel, because it was larger.
One of the kids I worked extensively with is 21 years old. And will still fall for this. He, unlike the recruit in the above anecdote, can read. I and his other tutors probably spent dozens of hours over several years trying to teach him to distinguish coins from one another. He has a high school diploma.
I know another young man. I didn’t work with him personally. I was cornered by him at a Christmas party when he kept trying to hold my hand. He was 18. Barely verbal. Was led around by para-educators in high school by the hand. Never learned to read beyond recognition of the alphabet and his own name, as far as I know. He, too, has a diploma.