Do You Really Control Your Actions?
One of the most provocative experiments in neuroscience—the Libet experiment—showed that your brain activity predicts your decisions before you're consciously aware of them. Does this mean free will is an illusion? Or is there more to the story?
"We must investigate two great mysteries, which might be called the sphinxes of the science, and which are deep enough to tax our intelligence to its utmost."
— Gottfried Wilhelm Leibniz
Leibniz's Two Great Mysteries:
- The Composition of the Continuum — How does the continuous emerge from the discrete? How can indivisible points form extended space?
- Freedom and Necessity — How can human actions be free when everything in nature follows deterministic laws?
Our Focus: This research addresses the second sphinx—the profound mystery of free will and human agency. When exactly does an action become "yours"? At what moment does necessity give way to agency?
The Libet Experiment: When Do You Decide?
In the 1980s, Benjamin Libet made a startling discovery: when you freely decide to move your finger, your brain shows activity (called "readiness potential") about 350ms before you consciously feel the urge to move.
This sparked decades of debate: If your brain "decides" before you're aware, are you really in control?
The free will debate continues: When does an action become "yours"?
But Wait—There's Another Critical Moment
Try this: Decide to move your finger, but at the last moment, try to stop. There's a point—about 200 milliseconds before you move—when it's too late to cancel. Your brain has already committed. What if we could detect that exact moment? And what if that moment is when you start feeling "I did that"?
The Mystery of "I Did That"
When you do something voluntarily—like pressing a button—you feel like you caused it. That feeling of control is called your sense of agency. But when exactly does your brain decide "this action is mine"?
Every voluntary action has two parts: Intention (before you move) and Agency (the feeling of control you have afterward)
The Point of No Return
Research shows there's a critical moment—roughly 200 milliseconds before you physically move—when you can no longer cancel the action. It's like your brain has already said "we're doing this" even though your finger hasn't moved yet. This project asks: Is that the moment when you start to feel in control?
The Hypothesis
If an outcome (like a sound) happens after the "point of no return" but before you physically move, will you still feel like you caused it?
Once you cross the point of no return, your brain might treat the action as "already happening"—even before you move. So if something happens in that brief window, you should still feel responsible for it.
How Do We Test This?
We built a brain-reading system that can detect before you move. Here's how:
Participant wearing an EEG cap to read brain activity, with their hand on a button
Step 1: Teach the Computer to Read Your Brain
First, we record brain activity while people press a button whenever they want. The computer learns to recognize the brain pattern that appears right before they move.
During training, participants make self-paced button presses. Each press makes a sound. We record their brain activity to teach the AI.
How the AI Learns
Brain signals are broken into small time windows and analyzed
Signals from multiple brain areas are combined to make predictions
Step 2: Test the Timing 🔄 In Progress
Once the system can predict when you're about to move, we trigger a sound at different times—sometimes before the point of no return, sometimes after. Then we ask: "How much did you feel like you caused that sound?"
The trained system watches your brain in real-time. When it detects you're about to move, it triggers a sound at varying times. After each trial, you rate how much control you felt.
What We Found (So Far)
The system achieved over 90% accuracy in detecting when people were about to move—before they actually did
✅ It Works!
We can reliably detect when someone is about to press a button just by reading their brain activity—before they move.
⚡ Fast Enough
The system updates every 20 milliseconds, making it quick enough to trigger outcomes within that critical 200ms window.
🔄 Currently Testing
The real-time experiment is now underway! We're testing whether timing truly affects your feeling of control—stay tuned for results.
Why This Matters
🤖 Better Brain-Computer Interfaces
If a robotic arm or computer responds too early to your brain signals, you might feel like it's controlling you instead of the other way around. Understanding the timing of agency helps us design systems that feel natural.
🧠 Understanding Free Will
When exactly does an action become "yours"? Is it when you think about it, when your brain commits, or when you physically move? This research helps answer fundamental questions about consciousness and control.
⚖️ Ethics & Responsibility
If a brain-computer interface acts on your detected intentions before you consciously decide, who's responsible for the outcome? Understanding agency timing is crucial for legal and ethical frameworks.
Master's Thesis
Hamed Ghane
MSc Brain and Cognition · Pompeu Fabra University · 2023
Supervised by Prof. Salvador Soto Faraco