Very interesting, and I think this part sums up the crux:

“The researchers believe that you can only analyze the raw responses because, statistically, any sequence is equally likely to occur, so where do you draw the line?”

I’d say that, as it is a psychological study, making claims about a human behavior, treating humans as pure random number generators without considering _intent_ is a mistake.

It is entirely possible that older people fill in more “questionable” responses because they can’t be bothered with the study, and that this causes the “decline” in ability as people age.

But we don’t know for sure, because it was never investigated. Thus, the biggest problem is the original study not even bringing this into light, even though it appears the original authors were aware of it.