Thinking about thinking: SCIoI member John-Dylan Haynes on thought, free will, and intelligence

By: Maria Ott

At Science of Intelligence (SCIoI), researchers are working to understand the principles of intelligent behavior, across species, systems, and scales. Neuroscientist John-Dylan Haynes, a PI at SCIoI, studies what happens in our brains, especially in moments we associate with thought. How do thoughts emerge? What happens in the brain when we make decisions, feel emotions, or consciously think of nothing at all?

This article is based on John’s recent interview with Deutschlandfunk Kultur, where he spoke with Ulrike Timm about his research and how it intersects with philosophy, technology, and everyday experience. You can listen to the full conversation here.

From math puzzles to mind reading: decoding the brain’s inner workings

From early on, John was curious about what happens in the brain when we get stuck on a problem and suddenly have a breakthrough moment. As a child, he’d get up from a math exercise, fix his bike—and plopp, the solution would come to him. Years later, as Professor of Neuroscience at Charité and Humboldt University and PI at SCIoI, he investigates these flashes of insight in controlled settings, using brain imaging and machine learning.

His lab’s core work involves decoding brain activity: placing volunteers in a scanner and analyzing how specific thoughts, like “dog,” “drill,” or “piano”, light up the brain in distinct patterns. These patterns can be fed into algorithms, allowing computers to learn to distinguish between them. It’s a far cry from telepathy, but it’s surprisingly effective. “Each thought leaves behind a characteristic fingerprint,” John explains.

Still, there’s a catch: the method only works if researchers already know what the person is thinking. If someone is daydreaming freely, their mental state can’t be decoded without reference points. This makes the method powerful in structured tasks but limited for spontaneous inner experience. “It’s like teaching a computer to recognize apples and pears,” John says. “But if someone suddenly thinks about something we’ve never trained the system on, it’s blind.”

Challenging free will and countering the brain-tech hype

In the interview, John also discusses the ethical and philosophical implications of this research, issues that are deeply embedded in SCIoI’s interdisciplinary structure. Having studied philosophy himself, he often reflects on what it means to decide freely, and what the brain’s quiet preparations for decisions say about free will. His experiments show that the brain begins to get ready for a decision seconds before we become aware of it, challenging our intuitive sense of agency.

And then there’s the hype. From Elon Musk’s brain chips to exaggerated claims by tech firms, John sees a need for grounded, science-based communication. “There’s enough that’s fascinating in brain research,” he says. “We don’t need to promise the impossible.” This is one reason he wrote the book Fenster ins Gehirn, where he explains in plain terms what’s really possible, and what isn’t.

For John, thinking about thinking is still a source of daily fascination. Whether it’s decoding decision-making or reflecting on how individual memory and meaning shape the neural trace of a word like “dog,” his work doesn’t aim for spectacle, it aims to understand. And within Science of Intelligence, it’s exactly that kind of curiosity-driven research that helps build a fuller picture of what intelligence might be.

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