Caltech researchers have estimated the speed of human thought to be a mere 10 bits per second, a data rate so leisurely that it underscores the need for further research into brain function and calls into question claims about brain-computer interfaces and artificial intelligence.
In a paper [PDF] titled, “The Unbearable Slowness of Being: Why do we live at 10 bits/s?,” published in the journal Neuron on Tuesday, Jieyu Zheng, a Caltech graduate researcher, and Markus Meister, professor of biological sciences, explore the cognitive conundrum of the human brain.
Why, they ask, does the inner brain process thought at about 10 bits per second while the outer brain – which handles sensory information – operates 100 million times faster, at about 10^9 bits per second.
The authors muse, “The stark contrast between these numbers remains unexplained and touches on fundamental aspects of brain function: What neural substrate sets this speed limit on the pace of our existence? Why does the brain need billions of neurons to process 10 bits/s? Why can we only think about one thing at a time?”
Zheng and Meister arrived at the 10 bits/s estimate for the speed of thought by analyzing prior studies conducted over the last century of human behavioral throughput for various behaviors and activities. These include: binary digit memorization (4.9 bits/s); speech in 17 different languages (39 bits/s); listening comprehension in English (13 bits/s); object recognition (30-50 bits/s); StarCraft (10 bits/s); typing (10 bits/s).
This is consistent with prior work that suggests humans communicate at a rate of about 40 bits/s.
This also has implications when trying to estimate the storage capacity of the human brain, which the researchers say could be accommodated on a 5GB thumb drive, if a person absorbed data at a rate of 10 bits/s, 24 hours a day, for 100 years.
The Caltech authors observe that people like to think their inner lives are far too complex to be expressed in real-time speech, as allowed by a brain pipeline running at 10 bits/s. But that’s just an illusion, they say.
“Because we could engage in any one of the 2^10 possible actions or thoughts in the next second, it feels as though we could execute them all at the same time,” they state in the paper. “In practice, however, they happen sequentially.”
But this illusion about human mental throughput has consequences, they argue, because technologists believe it.
For example, Neuralink co-founder Elon Musk has described his brain implant company thus in a 2018 interview: “The purpose of neuro-link is to create a high bandwidth interface to the brain such that we can be symbiotic with AI, because we have a bandwidth problem. You just can’t communicate through your fingers. It’s too slow.”
Zheng and Meister don’t believe a high-bandwidth interface is necessary to communicate with the brain.
“Based on the research reviewed here regarding the rate of human cognition, we predict that Musk’s brain will communicate with the computer at about 10 bits/s,” they write. “Instead of the bundle of Neuralink electrodes, Musk could just use a telephone, whose data rate has been designed to match human language, which in turn is matched to the speed of perception and cognition.”
Neuralink did not respond to a request for comment.
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Meister in email told The Register that he believes the tech community should revisit its requirements for direct brain communication in light of the speed of thought.
“[Musk] says in that interview, he wants this interface to be available for everyone, the man on the street,” Meister said. “That’s al