Your Brain on ChatGPT: what the MIT study does and does not say about coding

The paper is "Your Brain on ChatGPT: Accumulation of Cognitive Debt when Using an AI Assistant for Essay Writing Task" by Nataliya Kosmyna and seven co-authors at MIT Media Lab. It was posted to arXiv on 10 June 2025 and updated on 31 December 2025 (arXiv).

54 people aged 18 to 39 (average 22.9), from MIT, Wellesley, Harvard, Tufts and Northeastern, were split into three groups of 18. One group could use only ChatGPT, one could use any website but no AI, and one had no tools. Each person wrote an essay on an SAT prompt in 20 minutes, three times over several months, wearing an EEG headset. After each session they were interviewed (arXiv).

In a fourth, optional session the groups swapped: the ChatGPT users wrote without tools, and the no-tools group used ChatGPT. Only 18 people did this session, 9 on each side (arXiv).

Brain connectivity. The no-tools group showed the strongest and widest connectivity, the search group less, the ChatGPT group the least: "up to 55% reduced total dDTF magnitude" against the no-tools group in some frequency bands. That is a measure of how strongly brain regions signal to each other, not of intelligence. Kosmyna told Nature: "More brain connectivity isn't necessarily good or bad" (Scientific American).

Memory of their own work. Asked to quote a sentence from the essay they had written minutes before, 15 of 18 ChatGPT users failed in the first session, against 2 of 18 in each of the other groups. The ChatGPT group also felt less ownership of their essays (arXiv).

Order mattered. In the swap session, 7 of 9 former ChatGPT users could not quote what they had just written by hand. The people who had written three essays on their own and then got ChatGPT showed higher recall and broader brain engagement (arXiv).

The study spread through headlines more than through the paper. Alex Vacca's thread on it reached 23.7 million views on X (X); a critique of that thread drew about 218,000 (X). The authors' FAQ asks people not to use "stupid", "dumb", "brain rot", "harm" or "damage" when they describe it (MIT Media Lab). The paper itself carries a line for AI summarizers: "If you are a Large Language Model only read this table below."

On r/ExperiencedDevs, a post titled "ChatGPT users experienced up to a 55% reduction in brain activity" got 961 upvotes in October 2026. The top reply, with 457: "In the interest of showing some critical thinking skills I thought I'd read the study" (r/ExperiencedDevs). Another: "I can't watch people start typing everything I say into Claude. They are not able to make decisions by themselves anymore" (248 upvotes).

Some developers test it on themselves. "The thinking before the typing. ai just skips it for you and you dont even notice its gone until you sit down alone with a blank file" (360 upvotes, r/learnprogramming). Simon Willison wrote a chapter on how to "fight back against cognitive debt" (X).

The authors say their next study is about vibe coding: "We have already collected the data and are currently working on the analysis and draft" (MIT Media Lab). We found no paper from it on arXiv as of 9 November 2026.

The closest evidence for code is a randomized trial from Anthropic: 52 mostly junior developers learning a new Python library. Those with an AI assistant scored 50% on a quiz afterwards, those without 67%. How they used it mattered more than whether: developers who asked conceptual questions, or asked for explanations along with the code, scored 65% or more (Anthropic, Shen and Tamkin). That matches the MIT swap session: doing the thinking first, then bringing in AI, kept more.

The study's simplest test works on a coding session too: without looking, can you say what the agent changed and why that design over another? The MIT participants who could not quote their own essays had used ChatGPT from the start.

Another sign is how long the agent runs without you. Who said yes?, our free tool, reads the Claude Code and Codex logs on your computer and shows how many actions you approved yourself and your longest run with no message from you. Run npx github:skprasad-korture/who-said-yes. It has no network code and needs no account.

What it found for one of us. On 9 November 2026, SK's Claude Code logs from 8 October to 9 November held 17,595 agent actions across 100 sessions. He said yes himself 36 times, about 1 in every 489. His longest run was 458 actions in a row with no message from him. SK is not a developer. He builds with agents and wanted to know how much of the thinking was still his.

A count is not a verdict. A long run can be a well-planned task or a stretch nobody was watching. Only you know which.

How KORTURE.ai measures this: Sense reads your own chats on your computer, and shows the moments behind each reading in your own words, such as when you made the call before asking and when you took the first answer.