Your Brain on AI

Your Brain on AI: What EEG Reveals About Cognitive Debt

A groundbreaking study by MIT researchers (Kosmyna et al., 2025) used EEG—and a digital obstacle course—to uncover the hidden cost of relying on LLMs versus traditional search or writing without tools.

⚙️ The Experimental Setup

• Participants (n = 54) were split into:

  • Brain‑only: wrote essays with no assistance.

  • Search engine: used Google.

  • LLM: used ChatGPT or similar.

• After three sessions, groups swapped tools to observe learning and rebound effects in a fourth session

🔍 Key Findings from the Study

1. Neural Connectivity Declines with AI Use

   • Brain‑only writers showed the strongest, most widespread EEG connectivity across alpha, beta, and delta bands.

   • Search engine users displayed moderate connectivity.

   • LLM-assisted writers had the weakest brain connectivity, indicating lower cognitive engagement

2. Switched Tool, Switched Brain

   • Participants moving from Brain‑only to LLM (Brain→LLM) showed increased visual and executive functions, similar to search engine users.

   • LLM-to-Brain participants, however, failed to regain strong connectivity, showing ongoing cognitive dampening

3. Lower Ownership & Recall

   • LLM users reported lowest sense of authorship, struggled to quote their own content.

   • Brain-only users showed full ownership and scored highest in essay coherence and originality .

4. Cognitive Debt Accumulates

   • Over 4 months, LLM users underperformed in writing quality, neural effort, and memory compared to other groups.

   • The study introduces “cognitive debt”—the gap between convenience and sustained mental engagement

💡 Why It Matters

• Tools reduce brain discipline: Like calculators teaching fewer math basics, LLMs reduce deep cognitive exploration.

• Effort fuels learning: True skill—writing, creating, reasoning—is nurtured through active struggle.

• Mindful adoption is vital: There’s value in AI—but only when paired with deep cognitive work, learning mechanisms, and periodic unplugging.

🔧 Practical Takeaways

• Limit AI use for drafting only—do heavy editing, recall work manually.

• Alternate brain states—rotate between “tool-on” and “tool-off” sessions.

• Track cognitive engagement—use shared reflection, memory tests, or short EEG-like metrics where possible.

✅ Final Word

AI is a powerful assistant—but not a replacement for human thought. MIT’s study warns: unbridled AI reliance erodes mental investment and depth. Enter the era of “Cognitive-First AI”—using tools to amplify but not replace human brilliance.