I have been thinking about this question in some depth.

It basically applies to any human brain and it has nothing to do with neurodivergence.

Think about a video game. There's a lot going on. There's millions of pixels on the screen. But when you know the game, your decisions are based on a very high level understanding of what's going on. Maybe, you recognize what NPC enemy you are facing and what move they are making. If there are 16 different enemies, then that's only 4 bits of information. If every NPC has 8 different moves, then that's only another 3 bits.

You make the high-level decisions based on very few bits of information. You implement the decisions by pushing buttons. When you are skilled, you don't have to think about the buttons, or what your fingers do. Some part of your brain is taking in a lot of information about what your fingers sense via touch, the angle of the joints (proprioception), and so on. Then a large number of muscles is controlled in perfect harmony to hit the keys.

The paper gives the estimate that our senses deliver 1 billion bits/s to the brain. But the higher level thinking has a throughput of only a little over 10 bits/s. I called it conscious thought but that's not exactly right. The paper talks about the "inner brain" and "outer brain".

Feeling flooded by information may have to do with lacking the necessary skill in preprocessing to extract the relevant information. In the video game example, I gave above, that would mean not knowing the possible enemies or their moves. It may also reflect a failure to prioritize appropriately. That is, only making the necessary information available to the decision-making process. That is said to be a factor in ADHD.

That feeling might also simply be an illusion, like a déjà vu.

Individual differences in throughput are probably related to intelligence but that's not related to neurodivergence. People who are perceived as intelligent, for example, use a bigger vocabulary. That is, they chose their words from a larger number of possibilities, which implies a higher information throughput all else equal. However, in terms of bits, that difference is certainly small.

10 bits means picking 1 out of 1024 possibilities. 11 bits allow 1 out of 2048 possibilities. Every bit doubles the number. More bit/s would either allow more different choices or twice as many decisions. Some people seem to think faster than others or seem to consider a bigger space of solutions in the same time. If their throughput is 3 bits higher than average, they would be able to think 8 times faster or consider 8 times more possibilities. Thinking about how fast people talk/write or what vocabulary they use, I think there's hardly anyone who's that much above average.

If the guesser wins routinely, this suggests that the thinker can access about 220≈1 million possible items in the few seconds allotted.

I'm not sure this premise is sound. Are there not infinitely more than 2^20 permutations of the game?

This would be true if the questions were preset, but the game, in reality, requires the guesser to make choices as the game progresses. These choices can be quite complex, relying on a well developed theory of mind and shared cultural context. Not all the information is internal to the mechanics of the game.

The unspoken rules of the game also require the thinker to pick something that can plausibly be solved. Picking something outlandishly obscure would be frowned upon. The game is partly cooperative in that sense.

If you were to reduce the game to "guess the number I'm thinking of between 0 and infinity", then it wouldn't be very fun, it would not persist across time and cultures, and you wouldn't be studying it. But you might get close to a 0% win rate (or...maybe not?).

I'd guess that most of the "few seconds" the thinker spends is actually to reduce the number of candidates to something reasonable within the context of the game. If that's true, it says nothing whatsoever about the upper bound of possibilities they are capable of considering.

Idea for further research: establish a "30 questions" game and compare win rates over time. Hypothesis: the win rate in 30 questions would fall to similar levels as with "20 questions" as players gained experience with the new mechanics and optimized their internal selection process.

our brain will never extract more than 10 bits/s

Aren't there real recorded cases of eidetic memory? E.g. The Mind of a Mnemonist. I have not re-read that book with a mind toward information theory, so perhaps I am overestimating/misremembering the true information content of his memories.

Think about a video game. There’s a lot going on. There’s millions of pixels on the screen. But when you know the game, your decisions are based on a very high level understanding of what’s going on. Maybe, you recognize what NPC enemy you are facing and what move they are making. If there are 16 different enemies, then that’s only 4 bits of information. If every NPC has 8 different moves, then that’s only another 3 bits.

You make the high-level decisions based on very few bits of information. You implement the decisions by pushing buttons. When you are skilled, you don’t have to think about the buttons, or what your fingers do. Some part of your brain is taking in a lot of information about what your fingers sense via touch, the angle of the joints (proprioception), and so on. Then a large number of muscles is controlled in perfect harmony to hit the keys.

The paper gives the estimate that our senses deliver 1 billion bits/s to the brain. But the higher level thinking has a throughput of only a little over 10 bits/s. The paper uses the terms “inner brain” and “outer brain” for that.