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Your Brain on ChatGPT: Accumulation of Cognitive Debt when Using an AI Assistant for Essay Writing Task
(arxiv.org)
This is a paper for a MIT study. Three groups of participants where tasked to write an essay. One of them was allowed to use a LLM. These where the results: 
The participants mental activity was also checked repeatedly via EEG. As per the papers abstract:
EEG revealed significant differences in brain connectivity: Brain-only participants exhibited the strongest, most distributed networks; Search Engine users showed moderate engagement; and LLM users displayed the weakest connectivity. Cognitive activity scaled down in relation to external tool use.
Oh neat, a new subclass of brainrot has been observed and defined.
I've been saying this for years:
One way to win the Turing test is if you make every human so much more stupid that it is easier for an 'AI' to pass the test.
Now that's out of the box thinking!
Unfortunately it is a massive negative sum solution to a game theoretic approach to passing a Turing test, but it is a solution.
Roughly on par with winning an arcade fighting game by actually punching your local opponent irl.