Scientists at Caltech have uncovered a surprising limit to human thought speed—just 10 bits per second—despite our senses absorbing data at a billion bits per second.
This discovery raises fascinating questions about how our brains filter information and why we process one thought at a time. The study suggests evolutionary factors may play a role, with early brains designed for simple navigation rather than multitasking.
Quantifying the Speed of Thought
Caltech researchers have quantified the speed of human thought and found it to be just 10 bits per second. In contrast, our sensory systems process information at an astonishing rate of a billion bits per second—100 million times faster than our thinking speed. This discovery opens up intriguing questions for neuroscientists, particularly why the brain can focus on only one thought at a time while simultaneously handling vast amounts of sensory input.
The study was conducted in the lab of Markus Meister (PhD ’87), the Anne P. and Benjamin F. Biaggini Professor of Biological Sciences, with graduate student Jieyu Zheng leading the research. Their findings were recently published in the journal Neuron.
Understanding Bits and Human Cognition
A bit is a basic unit of information in computing. A typical Wi-Fi connection, for example, can process 50 million bits per second. In the new study, Zheng applied techniques from the field of information theory to a vast amount of scientific literature on human behaviors such as reading and writing, playing video games, and solving Rubik’s Cubes, to calculate that humans think at a speed of 10 bits per second.
The Paradox of Brain Efficiency
“This is an extremely low number,” Meister says. “Every moment, we are extracting just 10 bits from the trillion that our senses are taking in and using those 10 to perceive the world around us and make decisions. This raises a paradox: What is the brain doing to filter all of this information?”
There are over 85 billion neurons in the brain, with one-third of these dedicated to high-level thinking and located in the cortex. Individual neurons are powerful information processors and can easily transmit more than 10 bits per second of information. But why don’t they? And why do we have so many if we’re thinking so slowly? Meister suggests that, given the discovery of this “speed limit” in the brain, neuroscience research ought to consider these paradoxes in future studies.
Another conundrum that the new study raises is: Why does the brain process one thought at a time rather than many in parallel the way our sensory systems do? For example, a chess player envisioning a set of future moves can only explore one possible sequence at a time rather than several at once. The study suggests that this is perhaps due to how our brains evolved.
Evolutionary Origins of Thought Processing
Research suggests that the earliest creatures with a nervous system used their brains primarily for navigation, to move toward food, and away from predators. If our brains evolved from these simple systems to follow paths, it would make sense that we can only follow one “path” of thought at a time. “Human thinking can be seen as a form of navigation through a space of abstract concepts,” Zheng and Meister write. The team emphasizes the need for future research into how this constraint—one train of thought at a time—is encoded in the architecture of the brain.
“Our ancestors have chosen an ecological niche where the world is slow enough to make survival possible,” Zheng and Meister write. “In fact, the 10 bits per second are needed only in worst-case situations, and most of the time our environment changes at a much more leisurely pace.”
Rethinking Brain-Computer Interfaces
The new quantification of the rate of human thought may quash some science-fiction futuristic scenarios. Within the last decade, tech moguls have suggested creating a direct interface between human brains and computers in order for humans to communicate faster than the normal pace of conversation or typing. The new study, however, suggests that our brains would communicate through a neural interface at the same speed of 10 bits per second.
Reference: “The unbearable slowness of being: Why do we live at 10 bits/s?” by Jieyu Zheng and Markus Meister, 17 December 2024, Neuron.
DOI: 10.1016/j.neuron.2024.11.008
Funding was provided by the Simons Collaboration on the Global Brain and the National Institutes of Health. Markus Meister is an affiliated faculty member with the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech.
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1 Comment
Ten bits per second? One thought at a time?
Those are both disproved by simple things like talking and driving at the same time, answering questions while on a phone conversation, catching thrown objects. Multiple, simultaneous tasks are common as are things like rapid analysis. I spent a career as a programmer; at ten bits per second I would still be working on my first complex program from 50 years ago.
I call BS on the whole premise.