This reminds me of the recurring pattern with every new medium: Socrates worried writing would destroy memory, Gutenberg's critics feared for contemplation, novels were "brain softening," TV was the "idiot box." That said, I'm not sure "they've always been wrong before" proves they're wrong now. Where I'm skeptical of this study: - 54 participants, only 18 in the critical 4th session - 4 months is barely enough time…
Critical thinking, forming ideas, writing, etc, those are too stuff that can atrophy if not used.
For example, a lot of people can't locate themselves without a GPS today.
To be frank I see it really similar to our muscles: don't want to lose it? Use it. Whether that is learning a language, playing an instrument or the task llms perform.