Sorry I can't provide more details--my wife found that information at the UC Berkeley psychology library whe she was a student and I first became interested in chess (1971).
Note that I brought this up in answer to Opti's query about what other factors besides IQ might affect chess ability.
^^ Don't think so, because with long lines, visualisation is inaccurate and chess is all about detail.
My (and your) visualization may be inaccurate, while Morphy's or Kasparov's is far more accurate, giving them some advantage over us.
It's just that current thinking tends to indicate or postulate that visualisation isn't dominant in chess calculation.
In the 1920s the French Chess Olympiad team was given a variety of mental acuity tests. Alekhine was on the team, as well as artist/chessplayers Marcel Duchamp and Man Ray. The only areas in which all those strong players scored in the 99th percentile were visualization and visual memory.
When you say "visualization and visual memory" - what exactly does that mean? "99 percentile in visualization and visual memory"? Visual memory is one thing, visualization would mean that you're imagining a picture in your mind. Nobody can really measure what someone else is visualizing in another person's mind and say "that person has a 99 percentile for that". That falls into the whole fallacy about iq a lot of people have - this assumption that you can simply measure things like visualization or intelligence - there's the number and there you go.
I also would bet good money it was "visual memory" they tested and you just threw "visualization and visual memory" in there to try to force your point.
Nobody said some sort of visualization wasn't important in chess players by the way, of course visualization of some sort must help, it just doesn't work like a movie of all the chess pieces going around a board would be in a good player's mind. That's the only point people are making here.
I also never heard of that study before, maybe there were other problems with it since otherwise people would have heard about it. Here's Carlsen remarking on how bad he is at such things.
https://www.youtube.com/shorts/Wc9hPxbDXWM
Oddly enough, I bet Carlsen might well be in the 99th percentile if he tried hard at it, the only point being made is that visualization isn't EVERYTHING, it's only one component. To be the best in the world you have to be 99 percentile at everything remotely relevant, and visualization and particularly visual memory is certainly some component to being a good chess player.