I started to run into trouble with the first example in the linked article: "this suggests that the thinker can access about 2^20 ≈ 1 million possible items in the few seconds allotted" Huh???? What's the logic behind this? Ah, I see. It makes a lot of assumptions about how the "thing" is selected and also about the actual number of bits communicated in a yes/no question.
Very likely the thinker can only access a relatively few items when asked cold and most of the time will be spent in doing a lot of processing about what will be an answer which will be hard to guess and maybe also constrain the answer to be within the shared experience of thinker and guesser* Treating that as simple random access is going to seriously misrepresent what's actually happening.
Also, even if the questions are posed as yes/no it's not necessarily easy to answer as yes or no. If, for instance the question is "Is it red?" it will be a good deal easier to answer if "it" is el Reg's banner rather than a terracotta pantile, somewhere between orange and red. Whatever the answer, the hesitation, intonation and facial expression of the answerer will convey more than one bit of information.
What else? Typing speeds? How many bits are actually needed to select a letter? A good deal more than they seem to think givern the number of muscles that need to be controlled with considerable recision. In fact most.if not all the tasks they measure are input or output tasks and depend on the rate at which things happen in the external world. There's a limit as to how fast the fingers can move in typing, how fast a pen might move to produce legible writing. Speech recognition needs a lot of processing to turn sounds into meaning and, of course there's a limit on how fast they can be spoken with fast speech putting an extra burden on the listener to sort out the badly articulated sound.
What may well be beyond measurement is the purely internal processing when problem solving. How many bits per second are involved in running through a lot of complicated ideas? How many bits is an idea?
* If that isn't done the guesser will routinely not win. Zheng and Meister may be biologists but, as another biologist I would have no problem thinking about biological objects outside their experience - and, of course, vice versa