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Scientists have finally quantified the brain’s speed limit in processing human thought, an advance that reveals why we are able to process only one thought at a time.
The human body’s sensory systems, including the eyes, ears, skin, and nose, gather data about our environments at a rate of a billion bits per second.
However, researchers have found that the brain processes these signals at only about 10 bits per second – a speed millions of times slower than the inputs.
The bit is the basic unit of information in computing with a typical Wi-Fi connection processing about 50 million bits per second.
The brain has over 85 billion neurons with a third of these involved in high-level thinking and located in the more developed cortex region of the outer brain.
Researchers assessed existing scientific literature on human behaviours like reading, writing, playing video games, and solving Rubik’s Cubes, and calculated that humans think at a speed of 10 bits per second – a number that they call “extremely low”.
The findings were published in the journal Neuron last week.
“Every moment, we are extracting just 10 bits from the trillion that our senses are taking in and using those 10 to perceive the world around us and make decisions,” research co-author Markus Meister said.
“This raises a paradox: What is the brain doing to filter all this information?” Dr Meister said.
Individual nerve cells in the brain are known to be powerful information processors, easily capable of transmitting over 10 bits per second of information.
However, the new findings suggest they don’t help process thoughts at such high speeds, making humans relatively slow thinkers unable to process many thoughts in parallel.
This prevents scenarios like a chess player being able to envision a set of future moves and only lets people explore one possible sequence at a time rather than several at once.
The discovery of this “speed limit” paradox in the brain warrants further neuroscience research, scientists say.
Scientists speculate that this speed limit likely emerged in the first animals with a nervous system.
These creatures likely used their brains primarily for navigation to move toward food and away from predators.
Since human brains evolved from these simple systems to follow paths, it could be that we can only follow one “path” of thought at a time in a similar way, according to researchers.
“Our ancestors have chosen an ecological niche where the world is slow enough to make survival possible,” they write.
“In fact, the 10 bits per second are needed only in worst-case situations, and most of the time our environment changes at a much more leisurely pace,” scientists say.
The findings suggest machines can eventually excel at any task currently performed by humans as their computing power doubles every two years.
“So the discussion of whether autonomous cars will achieve human-level performance in traffic already seems quaint: roads, bridges, and intersections are all designed for creatures that process at 10 bits/s,” scientists add.
“By that point, humans will be advised to stay out of those ecological niches, just as snails should avoid the highways,” they write.
