Impressive research but I can't help feeling like it's fundamentally flawed. The analysis considered "essay ownership" a property of LLM, Search, and Brain-Only participants, but what would have been more valuable is flipping all of the graphs based on percieved ownership levels. On average, less LLM users felt a sense of ownership, and this should not surprise anyone. The researchers lumped together people who let LLMs do all of the writing vs using LLMs constructive ways. What would have been more interesting is studying the LLM users who maintained a sense of owership, because then we could learn more way to use LLMs that potentially make us smarter.
I also feel like there's more to be said about LLMs fostering the ability to ask questions better than you might if you primarily used search. If the objective was to write, for example, about an esoteric organic chemistry topic, and a "No Brain" group of non-experts was only allowed to formulate a response by asking real-life experts as much as they can about the esoteric topic, then would users more experienced with LLMs come out ahead on the essay score? Understanding how to leverage a tight communication loop most effectively is a skill that the non-LLM groups in this study should be evaluated on.