The paradox is that sensory input processing is done at a speed 100 million times faster than the speed of thought * Principal Investigator: "At any given moment, we extract only 10 bits out of a trillion that our senses pick up and use to perceive the world around us and make decisions. What does the brain do with all this information it filters?"
Scientists at the California Institute of Technology (Caltech) have discovered a surprising limit to the speed of human thought – just 10 bits per second – even though our senses absorb data at a rate of a billion bits per second.
This discovery raises fascinating questions about how our brains filter information and why we only process one thought at a time. The study suggests that evolutionary factors play a role, as our early ancestors' brains were designed for simple navigation rather than multitasking.
Quantifying the speed of thinking
Researchers at Caltech 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 the speed of thought. The discovery raises intriguing questions for neuroscientists, most notably why the brain can focus on only one thought at a time while processing a vast amount of sensory input.
The research was conducted in the laboratory of Prof. Markus Meister (PhD '87), Professor of Biological Sciences at Caltech, and led by research student Jiayu Zheng. The findings were recently published in the scientific journal Neuron.
A bit is the basic unit of information in computing. For example, a typical Wi-Fi connection can process 50 million bits per second. In the new study, Zheng applied techniques from the field of information theory to a vast body of scientific literature on human behaviors, such as reading and writing, video games and solving the Hungarian Cube, and calculated that humans think at a rate of 10 bits per second.
The paradox of brain efficiency
“This is extremely slow,” says Meister. “At any given moment, we extract only 10 bits out of a trillion that our senses pick up and use to perceive the world around us and make decisions. This raises a paradox: What does the brain do with all this information it filters?”
The brain has over 85 billion neurons, with a third of them dedicated to higher-level thinking and located in the cortex. A single neuron is a powerful information processor that can easily transmit more than 10 bits per second. So why don’t they? And why are there so many of them if we think so slowly? Meister suggests that with the discovery of this “speed limit,” future neuroscience research should consider these paradoxes.
Research suggests that the earliest creatures with nervous systems 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 could follow one “path” of thought at a time. “Human thinking can be thought of as a kind of navigation in a space of abstract concepts,” write Zhang and Meister.
The team emphasizes the need for future research into how this limitation – one thought pathway at a time – is encoded in the brain’s structure.
“Our ancestors chose an ecological niche where the world was slow enough to make survival possible,” write Zhang and Meister. “In fact, the 10 bits per second are only needed in extreme situations, and most of the time our environment changes at a much more leisurely pace.”
Rethinking brain-computer interfaces
The new quantification of the speed of human thought could shake up some of the science fiction scenarios of the future. Over the past decade, tech moguls have proposed creating a direct interface between human brains and computers to enable communication faster than the speed of normal conversation or typing. However, new research suggests that our brains will communicate via a neural interface at the same rate of 10 bits per second.
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