I came across a fascinating article in the March 2025 issue of Scientific American, "Brains produce thoughts surprisingly slowly." (Online title: "The Human Brain Operates at a Stunningly Slow Pace.") You can read the article via this PDF file.
Download The Human Brain Operates at a Stunningly Slow Pace | Scientific American
Often you hear that the human brain is the most complex entity in the known universe with its 80 billion or so neurons tied together with trillions of interconnections. That may be, but this impressive product of evolution works much slower than the smart phones most of us carry around. The article starts off with:
The brain is sometimes called the most complex machine in the known universe. But the thoughts that it outputs putter along at a trifling 10 bits per second, the pace of a conversation
People often feel that their inner thoughts and feelings are much richer than what they are capable of expressing in real time. Entrepreneur Elon Musk is so bothered by what he calls this “bandwidth problem,” in fact, that one of his long-term goals is to create an interface that lets the human brain communicate directly with a computer, unencumbered by the slow speed of speaking or writing.
If Musk succeeded, he would probably be disappointed. According to recent research published in Neuron, human beings remember, make decisions and imagine things at a fixed, excruciatingly slow speed of about 10 bits per second. In contrast, human sensory systems gather data at about one billion bits per second.
This biological paradox, highlighted in the new study, probably contributes to the false feeling that our mind can engage in seemingly infinite thoughts simultaneously—a phenomenon the researchers deem “the Musk illusion.” Study co-author Markus Meister, a neuroscientist at the California Institute of Technology, says that “the human brain is much less impressive than we might think. It’s incredibly slow when it comes to making decisions, and it’s ridiculously slower than any of the devices we interact with.”
Of course, this doesn't diminish the importance of what we humans have been able to create and accomplish: cathedrals, air travel, quantum physics, art of all kinds, novels, movies, microwave ovens, the scientific method, and so much more.
In fact, those accomplishments seem even more impressive now that the researchers have been able to accurately estimate the processing speed of the human brain.
Meister and Zheng collated data from research across different fields, including psychology, neuroscience, technology and human performance. They used this information—from the processing speed of single neurons to the cognitive prowess of memory champions—to run many of their own calculations so they could make comparisons between studies.
From research spanning nearly a century, they found that human cognition has repeatedly been measured as functioning at between about five and 20 bits per second, with a ballpark average of around 10 bits per second. “This was a very surprising number,” Zheng says. Based on this finding, she adds, she and Meister also calculated that the total amount of information a person can learn across their lifetime could comfortably fit on a small thumb drive.
Human sensory systems such as sight, smell and sound, in contrast, operate much faster, the authors found—at about 100,000,000 times the rate of cognition. “When you put these numbers together, you realize there’s this huge gap,” Meister says. “From that paradox comes interesting new opportunities for science to organize research differently.”
The rich information relayed by our senses also contributes to a false notion that we register the massive amount of detail and contrast all around us. But that’s “demonstrably not true,” Meister says. When people are asked to describe what they see outside the center of their gaze, they “barely make out anything,” he adds.
Because our eyes have the capability to focus on any detail, he continues, “our mind gives us the illusion that these things are present simultaneously all the time,” even though in actuality we must focus on specific visual features to register them. A similar phenomenon occurs with mental ability. “In principle, we could be having lots of different thoughts and direct our cognition in lots of different ways,” Meister says. “But in practice, we can have only one thought at a time.”
For me, that was the key takeaway of this article -- that my brain, your brain, and everybody's brain can only do one conscious thing at a time. So when people claim that they can multitask, such as watch television and also send text messages, actually they are switching between the two activities, not doing both at the same time.
Meister and his co-author Jieyu Zheng, a doctoral candidate in neurobiology at Caltech, also highlight in their paper that our brain can do only one thing—slowly—at a time. Even if Musk managed to hook his brain up to a computer, Meister says, he still wouldn’t be able to communicate with it any faster than he could if he used a telephone.
...Another important unanswered question, Meister says, is why the human brain can do only one thing at a time. “If we could have 1,000 thoughts in parallel, each at 10 bits per second, the discrepancy wouldn’t be as big as it is,” he says. Why humans are incapable of such mental multitasking is “a deep mystery that almost nothing is known about.”
Since I'm a big fan of mindfulness, I already was doing my best to do one thing at a time. Now I know that not only is this feasible, it's the only way my brain operates. But the illusion of multitasking remains, such as when I think that I can jot something down on the pad of paper I carry around in my car, while simultaneously being able to drive safely.
After reading this article, now I'll be more inclined to just do one thing at a time, even if I feel like I'm capable of doing several things. However, the article doesn't speak about whether physical actions and mental cognition obey the One Thing at a Time rule.
For example, typically I read a magazine while I'm brushing with an electric toothbrush. I can read at the same time I'm brushing my teeth. But I wouldn't be able to add numbers together while reading. It might well be that physical actions, which I'm aware of via perceptions, are easy to do while thinking of something else because our sensory systems are hugely faster than our cognition.
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