So here's my 2 cents of anecdotal evidence with a couple of examples. I've only been doing this for 5 weeks, but I feel like I wanted to get this down in writing so I don't forget to keep observing it later.
I did my 6th and final pass through set A of Bain today. Here's the final results of each pass in histogram form. I forgot to record the results of pass 4.
Very nice and steady improvement, if you remember my caveat about pass 1 being hand-timed instead of Anki-timed. I completed 89.06% within 15 seconds with only a 6.25% error rate. When going through this pass, I felt something different about my process. The first few passes, a lot of your answers are done right from short-term memory "oh, I got this wrong 2 days ago, the answer is Ne5" followed by a verification of the moves that lead to the solution. You're reminded of the solution rather than finding the solution. Pass 6 was done 13 days after pass 5. I noticed I wasn't spitting out the answers from memory on most of the diagrams. Sure, there are some diagrams that are so unique in this book that you just know "Rh6 wins here" because it doesn't resemble any other pattern in the book. What I noticed was I was being drawn to certain parts of the board and looking for the right pieces to attack and which ones of mine would do the attacking. It was more of an instinctual gut feeling. It feels different than accessing your short term memory for the right answer.
Here's an example:
Black to move
This problem appears in many forms throughout the book with both white and black to move. When I first saw the problem, I don't remember having any specific memory of it. I was just drawn to the bottom left part of the board and said "Oh, I need a rook check here". I glance up and see the rook and know the solution. The entire process was a couple of seconds. More importantly, I solved this problem on pass 6 faster than I had on any other pass of this specific problem. Most of my other passes took me in the 20 to 30 second range to see the answer. This time it was under 10. The reason it even took that long was because I actually stopped to marvel at my thought process and made a mental note to blog about this. Having done similar problems of this type in other sets drew me to the right answer almost immediately. Of course, this isn't really saying anything since we probably agree that puzzle training makes you better at puzzles. It's like the idea that football drills make you better at the drill, but not necessarily playing football. But I definitely "feel" like my solution is coming from a different place. It feels exactly like I do at work when someone comes to me with a troubleshooting problem and I instinctively know where to look for the solution.
So on to my next example. I was randomly looking around the blogosphere and came across this position of a missed tactic from The Back Rank.
White to move
I recognized the idea of Bh6 right away. Even in my high school days I knew that pattern well, along with the dreaded knight fork. Of course the d4 bishop makes it all moot, but I saw the idea of sacrificing the exchange for a pawn and an attack on the king. After about 15 seconds I didn't see a forced mate or material advantage so I moved on with reading the rest of his post. As a curiosity I put the position in Houdini and had it play through a few moves to get an idea of technique. After playing around a bit with some lines I eventually ended up in a position that looked something like this (from memory so might not be 100%):
White to move
Twenty years ago, my thought process would've been something like this, at best:
"I'm up material so I want to trade queens." From there I probably would've looked at a dozen different queen and rook moves trying to force a queen exchange or check mate. I figure there would be about 3 equally likely outcomes to this game.
- He drops the queen or trades it.
- I drop my queen or rook
- I get back rank mated
Rather grim since 2 of the scenarios are bad for me. I turn a win into a draw or loss. #2 certainly wasn't without precedent. I remember playing in a team tournament and going into what probably was a drawn rook and pawn endgame. I lost my rook to a skewer and eventually the game.
My thought process was a lot simpler this time:
"Qe1 drops my rook but is a forced tradeoff of his remaining heavy piece. The King and Pawn endgame is a win for me 100,000 times out of 100,000".
Qe1 was the 1st move I thought of and it was almost instantaneous. I knew that I wanted to play that right away. Houdini says I have mate in 11 if I start with c5, but why bother with the complications?
I'd venture to say the inspiration for that move came from Pandolfini's Endgame Course:
White to move