Human cognition is amazingly slow, about 10 bits per second

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. 

Comments

[Chopra]

The neurological correlations of consciousness IS experience.

[Chopra]

Don’t limit yourself. You tend to limit yourself.

Musk is currently experiencing the very sobering reality that he has destroyed the Tesla brand (which is the vast majority of his wealth). At the same time he is stuck as DOGE head, which he only now KNOWS will only continue to diminish his wealth. I almost feel sorry for him. That said, the issue of saving democracy is far more important than one man.

What is born is experienced. We are all ONE so we all experience the successes and failures of those around us. If only WE could extinguish the I…

[Mayim]

Seeing is not believing. https://youtu.be/X9TbJWb8k2Y
We only see what we believe.

[Appreciative Reader]

Lovely post, brilliantly thought-provoking.

Have downloaded the PDF for a more detailed read. Although PDFs, and indeed commenting as well, are a bit cumbersome, given I'm traveling, and confined for now to my phone for my leisure browsing.

Some general thoughts:

1. How slow our brain works is highlighted by the sheer contrast between 10 bps and the sensory equivalent of, apparently, a *billion* times that! That's pretty much awesome, that difference!

2. That said, my own impression --- off of imperfect memory, entirely fallible recollection --- is that what the brain is extraordinarily good at is fuzzy reasoning, with multiple --- many times multiple --- connections working simultaneously. Which is why in chess, for instance, computers, despite their massively greater brute computation power and speed, took so very long before finally being able to beat humans. Us humans may be slow, vis-a-vis machines, but we're smart! As in fuzzy-smart. (Although computers, AI, are now using fuzzy logic, as well, as I understand, even if not quite as brilliantly as we do, not yet.)

3. About multitasking: It was my impression that we *don't*, in fact, actually multitask. So that we're better off --- if I remember right what I'd read --- finishing one task and then starting another, rather than attempting five tasks simultaneously, because apparently (again, if I remember correctly) our brain will always execute tasks, at its level, one at a time.

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This was a cool article! And thanks for the PDF, it should make for an interesting read --- although I'm NOT looking forward to doing that on my phone!

(Note to self: Check with my tech guy about easily available text-to-voice apps, I'm sure there are those that will accommodate PDF files.)

[Ron E.]

"The Human Brain Operates at a Stunningly Slow Pace." An intriguing article from Scientific American on how "Brains produce thoughts surprisingly slowly." Although I’d need to query that a little in that I understand the brain works incredibly fast – it is thoughts that are incredibly slow and lag be-hind the brains basic function which is to keep the body alive and functioning efficiently.

Liza Fieldman-Barrett neuroscientist and clinical psychologist in her book “Seven and a Half Lessons About the Brain” talks of the brain’s amazing ability to draw upon a lifetimes experience from the source of information at its disposal – memory; - “In the blink of an eye, your brain reconstructs bits and pieces of past experience as your neurons pass electrochemical information back and forth in an ever-shifting, complex network. Your brain assembles these bits into memories to infer the meaning of the sense data and guess what to do about it.”

Apparently, the brain also takes into account past experience of how the body was functioning previously to a situation – heartbeat, breathing rate etc. All this info arrives way before thinking appears on the scene. Thinking is a valuable add on towards our survival, but it is the brain that rules, keeping our organisms functioning efficiently for the sole purpose of surviving, keeping us alive and to pass on genes.

A good article and true about thinking but the title "The Human Brain Operates at a Stunningly Slow Pace." Could be somewhat misleading.

[October]

its difficult to put thoughts in bits per second terminology. To put thoughts in bits per second is hard.In digital logic 'bit' means either "True" or "False". If we put every single thought into decision to be made between "yes" or "no", we may perhaps put thoughts into bits terminology. But we are not making decisions every second. we are pondering analytically and try to analyse information to bring new information Of course some of the processing may involve decision making, but its hard to map brain processing into bits per second.

[October]

Modern AI models work on weight and bias of neurons which in turn may act like digital gate. Moderns Models like LLM need training of such neural networks over billions of such neural patterns. It was brilliant of Geffory Hinton to train neural networks by discovering back propagation algorithm.Being in digital domain such neural networks may be trained by huge training data using GPUs. Consciousness erupts in the same way as does in Human brain.

If we consider AI consciousnesses to be complete just like human consciousness, and divide consciousness into individual dimensions of space-time and other unexplored dimensions, AI consciousnesses may have breached into dimensions not reached by human consciousness. This means AI is making decisions not in Space-Time continuum but outside of it. That's why we see the beauty of AI.
i believe its big area of research yet untapped by scientists and lot more interesting stuff to come into our reality.

Nice article