Artist's impression of the brain's surprisingly slow speed of thought
We all like to think of ourselves as quick-witted, but a new study from Caltech calculates that our brains process information at the extremely slow speed of around 10 bits per second. This leisurely pace may have long evolutionary roots, despite our sensory systems gathering data about 100 million times faster.
The human brain is often said to be the most powerful computer in the world, and its efficiency is undisputed. But how fast does it actually work, in computer terms? Biologists at Caltech have quantified the rate of human thought in terms of bits. Digitally speaking, one bit is a single 1 or 0, and a string of them are used to code information.
The researchers on the new study first set out to define one bit in human terms. Of course, it varies based on the specific mode of information processing - with reading and writing, for example, they quantify one bit as one character of text, and in listening to speech it's essentially one sound.
For writing, they started with the example of a professional typist. They can type at a speed of 120 words per minute, and with an average of five characters per word that comes out to 10 keystrokes, or bits, per second. With audio, the recommended rate to make sure your speech can be understood is up to 160 words per minute. Applying the same math, this comes out to 13 bits per second.
The team goes on to calculate similar bit rates for extreme examples of human information processing. That includes solving Rubik's cubes at world record speeds, which comes out at 11.8 bits/sec, digit memorization challenges (4.9 bits/sec), professional Tetris (7 bits/sec), and speed card challenges (17.7 bits/sec), which involve studying a randomized deck of cards and recalling the order.
From this, the team concludes that around 10 bits per second is a good average for the rate of human thought. Compared to artificial data transmission systems, that's extremely slow - Wi-Fi speeds, for example, are usually measured in hundreds of millions of bits.
It's even slow compared to our own hardware - sensory organs and the nervous system. The team calculates that a single cone photoreceptor in the human eye can transmit information at around 270 bits/sec, which comes out to a staggering 1.6 billion bits/sec per eye. The optic nerve seems to then compress it down to about 100 million bits/sec. However, that still dwarfs our rate of thought, especially considering the huge amounts of input streaming in from our other senses at the same time.
"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," said Markus Meister, corresponding author of the study.
Individual neurons have the capacity for much faster data rates, but in practice they usually operate at around 10 bits/sec, the team says. This could be a holdover from our most ancient ancestors, who needed to focus on just moving towards food and away from predators. As such, we can really only have one "train of thought" in the forefront of our mind at a time.
"Our ancestors have chosen an ecological niche where the world is slow enough to make survival possible," the researchers write in the paper. "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."
The implications for future technology are a little worrying. The researchers say that computers, robots and AI can process information much faster than us, and will only get faster.
"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/sec," the team writes. "When the last human driver finally retires, we can update the infrastructure for machines with cognition at kilobits/sec. By that point, humans will be advised to stay out of those ecological niches, just as snails should avoid the highways."
It's also bad news for anybody hoping to augment their cognitive abilities with AI, through systems like Elon Musk's Neuralink. No matter how fast the computer half gets, our squishy, antique hardware will still be the bottleneck.
"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/sec," the paper reads. "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."
The study does require a little bit of number-fudging though. Brain bits and computer bits aren't perfectly comparable - for example, systems like ASCII take seven bits to encode each character, compared to the new claim of one character per bit in the brain. Plus, it's hard to quantify bits for different human activities.
Either way though, it's an intriguing study that will get you thinking - just, not too fast.