Of the more than 85 billion neurons in the brain, roughly one-third are present in the cortex, the outermost layer of the brain, and are in charge of complex thought. Each neuron can transmit over ten bits of information per second and is highly skilled at processing information. Why don’t they do it, then? And why do we still think so slowly if we have so many neurons?
Researchers at Caltech have analyzed how quickly people think by applying information theory techniques and examining a wealth of studies on human activities such as reading, writing, playing video games, and solving Rubik’s Cubes.
Caltech researchers have measured the speed at which humans think: just 10 bits per second, while our sensory systems collect data at a rate of one billion bits per second—100 million times faster. This discovery raises new questions for neuroscientists, mainly why we can only focus on one thought at a time when our senses can process thousands of inputs simultaneously.
Laboratory of Markus Meister (PhD ’87) said, “This is an extremely low number. Every moment, we extract just 10 bits from the trillion that our senses are taking in and use those 10 to perceive the world around us and make decisions. This raises a paradox: What is the brain doing to filter all this information?”
Given the discovery of this “speed limit” in the brain, Meister suggests that neuroscience research should consider these paradoxes in future studies.
Another question the study raises is why the brain can only process one thought at a time rather than handle multiple thoughts simultaneously as our sensory systems do. For example, a chess player can only consider one potential move at a time, not various options.
The researchers suggest this limitation may be linked to how our brains evolved. Early creatures with nervous systems used their brains for simple tasks like navigating toward food or away from danger.
As our brains evolved, it made sense that we could follow one “path” of thought at a time, just as early brains followed one path at a time in their environment.
Authors noted, “Human thinking can be seen as a form of navigation through a space of abstract concepts.”
The study highlights the need for future research into how this constraint—one train of thought at a time—is encoded in the brain’s architecture.
Authors noted, “Our ancestors adapted to an environment where the world moved slowly enough that survival was still possible, even with limited processing power. The study suggests that the 10 bits per second of thinking are only really necessary in high-pressure, worst-case scenarios. Most of the time, our surroundings change at a much slower, more manageable pace.”
The new measurement of the speed of human thought could challenge some science-fiction visions of the future. Recently, tech leaders have proposed creating direct connections between human brains and computers to enable faster communication than normal conversation or typing. However, the study suggests that our brains would still communicate at the same slow pace of 10 bits per second even with such a brain-computer interface.
Journal Reference:
- Jieyu Zheng, Markus Meister. The unbearable slowness of being: Why do we live at 10 bits/s? Neuron DOI: 10.1016/j.neuron.2024.11.008
