Every few weeks there is a headline saying AI is rotting our brains, and a reply saying it is just a calculator for words. Both are wrong in the same way: they treat "using AI" as one thing. The research I went through points to something much more useful. The same tool can make you weaker or stronger, depending on one thing: whether the AI is doing the part of the work that was supposed to make you better. So instead of arguing, here is a way to sort every task you give an AI into three categories, with the evidence for each, and something you can copy.
Category 1: the effort IS the point. Do these with no AI involved. There was a small experiment done by MIT Media Lab's called "Your Brain on ChatGPT" (Kosmyna and colleagues, 2025). Fifty-four people wrote essays, either with an LLM, with a search engine or with only their own head, while EEG measured their brain activity. The brain-only group showed the strongest connectivity, the search group was in the middle and the LLM group was the weakest, and the LLM group also felt the least ownership of what they wrote. It is a small preprint on one task, so it does not prove your brain is damaged. But it does show something simple: when the AI writes, you stop doing the thinking while it happens.
What to do: anything where the doing is the training- writing the essay, working out the problem, forming your own opinion, and the human things too: a birthday message, a condolence note, a text to a friend who is struggling. If you hand those over, you keep the output and lose the reason you were doing it.
Category 2: you are trying to get better. Try first, and ask for hints only when stuck.
There was a PNAS study in 2025 with nearly a thousand high school math students. One group practiced with a normal chatbot, one with a version that was set up to give hints and not answers. Both did better during practice. Then the AI was taken away for the exam: the normal chatbot group did worse than students who never used AI, while the hint version largely avoided that. (PNAS later published a correction, so I won't quote a percentage, but the direction is what the authors report.)
Say you want to get better at design. Step 1: make the design yourself, even badly if you have to. Step 2: send it to the AI with this: "Look at my design. Score it from 1 to 10. If it is below 8, give me ONE vague hint, like a human art teacher would (something like "this feels too bright"), and do NOT tell me the fix." Step 3: fix it yourself and repeat. The AI is a coach who asks questions, not a ghost designer. There are free open source skills on GitHub made for exactly this kind of design feedback, for example the "frontend-design skill" in Anthropic's public skills repo.
Category 3: admin work that needs hours but no thinking. Give it fully to the AI.
There was a Microsoft Research and Carnegie Mellon survey of 319 knowledge workers in 2025. People who trusted the AI more than themselves reported using less critical thinking for the tasks that didn't need it at all. Notice what that implies: the problem is not delegating, it is delegating things that don't need your judgment. For tasks that do need your thinking, delegating is not fine, and checking the result is not enough.
The best example I have is planning a long family trip. It takes hours of looking at flights across sites, comparing hotels and reading reviews to avoid the bad ones. None of that grows your brain, you just open tabs until something is good. So let the AI take over in those admin tasks. Give any commands like: "Find 3 flight options from [city] to [city] on [dates] and 3 hotels for [number] people, ignore any hotel with consistent complaints in its reviews, and show me the total price of each before I decide." There are open source tools for this also like LetsFG in Claude's directory.
Put together: bucket 1 you do yourself, bucket 2 you do first and ask for hints, bucket 3 you give away. If you want a 5 minute exercise, open your last 10 AI chats and mark each one 1, 2 or 3. Most people I would guess find a few chats in bucket 1 or 2 that they were handing away without thinking about it, and a lot of bucket 3 work they were still doing by hand.
PS: Links to sources and tools are below-
MIT Media Lab, Your Brain on ChatGPT: https://www.media.mit.edu/projects/your-brain-on-chatgpt/overview/
Microsoft Research, impact of generative AI on critical thinking: https://www.microsoft.com/en-us/research/publication/the-impact-of-generative-ai-on-critical-thinking-self-reported-reductions-in-cognitive-effort-and-confidence-effects-from-a-survey-of-knowledge-workers/
PNAS, Generative AI without guardrails can harm learning: https://www.pnas.org/doi/10.1073/pnas.2422633122
frontend-design skill (Anthropic skills repo, open source): https://github.com/anthropics/skills/tree/main/skills/frontend-design
LetsFG (open source, flights and hotels): https://claude.ai/directory/letsfg