I agree, of course nobody can actually do this (barring mind-altering drugs or brain trauma, and even then, not voluntarily). But there are people on this thread an on the attached survey (https://news.ycombinator.com/item?id=49469365) who say that they can. Maybe it turns out that I have aphantasia after all and this is just an ability that I'm missing.

I am curious to see how many people say that they can do this to get some sort of baseline though.