Who's doing your thinking

Most of us have done it by now. A tricky email to a colleague, a message to a friend after a falling-out, the first paragraph of a report you’ve been putting off. You type a few words into an AI tool and, seconds later, there it is: clear, polite and better punctuated than anything you’d manage at the end of a long day.

And sometimes, reading it back, there’s a small, odd feeling. It’s good. It just isn’t quite you.

That feeling is worth paying attention to.

What the research is starting to show

In 2025, researchers at the MIT Media Lab asked 54 students to write essays over several months while their brain activity was measured. Some wrote with no help, some used a search engine and some used ChatGPT.

The ChatGPT group showed the lowest levels of brain connectivity of the three. More striking still, most of them couldn’t accurately quote a single sentence from the essay they had written minutes earlier, while almost everyone who wrote unaided could. The researchers called this “cognitive debt”: convenience now, with the cost paid later.

It’s a small, early study about essay writing, so it’s a signal rather than a verdict. But it isn’t the only one.

A survey of 319 knowledge workers by Microsoft and Carnegie Mellon University found that the more people trusted AI to do a task, the less critical thinking they reported putting in. The more they trusted themselves, the more they questioned what the AI gave them.

And a 2025 study of more than 600 people by Michael Gerlich at the Swiss Business School found that heavier AI use went hand in hand with weaker critical thinking, with younger users most affected. That’s a correlation rather than proof of cause, but the pattern keeps showing up.

What pilots already knew

Aviation has been here before. Autopilot made flying far safer and more precise. But in 2014, the UK Civil Aviation Authority warned that pilots mustn’t become over-reliant on automated systems, and called for more training to keep manual flying skills sharp.

The automation wasn’t the problem. Never practising without it was. A skill you don’t use quietly fades, and you tend to find out at the moment you need it most.

It isn’t about switching AI off

There was an encouraging finding in the MIT study too. Students who wrote on their own first, and only then used AI to revise, showed stronger brain engagement than before.

Order matters. Think first, then ask.

Used that way, AI becomes a sparring partner rather than a substitute. You bring the messy first thoughts, and it helps you tidy them, check them or argue with them. The thinking is still yours; the tool just sharpens it.

The thinking worth keeping

Some kinds of thinking are worth protecting, because they’re how we get to know ourselves:

• What you actually want. AI can list options. It can’t tell you which one matters to you.
• How you feel. It can describe a feeling beautifully. Only you can have it.
• Decisions about your own life and work. Ask it for information, and keep the choice.
• Words to the people who matter most. An imperfect message in your own voice is worth more than a polished one in nobody’s.
• Making sense of what went wrong. Reflection is where learning happens, and it can’t be done on your behalf.

This is also why, in coaching, I very rarely give people answers. That’s not me being coy. Psychologists have long known that we remember and act on ideas we’ve worked out ourselves far more than ones we’ve simply been handed. An answer you reach for yourself tends to stick. The thinking is the work.

A few questions to sit with

• What have you handed over to AI recently that you might want back?
• When did you last sit with a problem for ten minutes before reaching for help?
• If you read back your last few messages, would they sound like you?
• Which decisions in your life deserve your own slow, unhurried thinking?

Final thoughts

AI is one of the most useful tools most of us will ever have, and I’m not suggesting anyone stops using it. But a tool should make us more ourselves, not less.

So before you ask it something that really matters, give yourself five minutes with a pen. What do you think? Start there.

If you’re at a crossroads and would like space to work out what you really think, coaching is a good place to do it. You can book a free introductory call here.

Sources for the article

• Kosmyna, N. et al. (2025) Your Brain on ChatGPT: Accumulation of Cognitive Debt when Using an AI Assistant for Essay Writing Task, MIT Media Lab (arXiv 2506.08872)
• Lee, H.-P. et al. (2025) The Impact of Generative AI on Critical Thinking, Microsoft Research and Carnegie Mellon University
• Gerlich, M. (2025) AI Tools in Society: Impacts on Cognitive Offloading and the Future of Critical Thinking, Societies
• UK Civil Aviation Authority (2004) CAA Paper 2004/10, Flight Crew Reliance on Automation
• CAA statement on autopilot reliance (2014)
• Slamecka, N. and Graf, P. (1978) The Generation Effect, Journal of Experimental Psychology (on remembering what we work out ourselves)