Researchers at the California Institute of Technology are trying to calculate the speed of human thought. And the number they come up with is a slightly disconcerting 10 bits of information per second.
But what are we talking about here? Your mind might (surprisingly slowly, it turns out) assume that we are talking about “bits” like computer ones. In computer language, a bit can have one of two values, often represented by a binary digit—1 or 0. But that doesn’t correspond to the amount of information being transmitted, sometimes called a “shannon,” after Claude Shannon, who in turn is called the “father of information theory.”
“To understand the concept of information, it is essential to distinguish it from that of data. Here is an example. We have a friend who has just given birth, and we send her a message to ask her about the sex of the newborn. From our perspective, there is an equal chance that the baby will be a boy or a girl. Therefore, her response will send us exactly 1 shannon. To respond, she will probably send us a sentence made up of several characters, each represented by several bits. We will therefore receive several dozen bits of data for 1 shannon,” explains Vincent Gripon, associate professor at Télécom Bretagne.
“Our brain is used to this fact. It has been estimated that one hundred million bits of data per second are transmitted from the visual cortex to the deep regions of our neocortex. Most of this data is completely useless to us and, moreover, carries very little information.”
Scientists studying information theory have tried to quantify the information of various systems, including how much information is transmitted in each syllable of language and how much information there is in the entire observable universe. In doing so, they stumbled upon a little mystery: Our brains are constantly bombarded with sensory data at an incredible rate, estimated at 109 bits per second, yet our conscious thoughts process information at a much slower rate.
As you might expect, human thought is difficult to quantify. In an attempt to do so, the authors of a new study looked at the tasks people perform and the amount of information they process during them. One such task is manual text typing.
“A good typist can type up to 120 words per minute. If each word is considered to be 5 characters, this typing speed corresponds to 10 keystrokes per second. How many bits of information does that represent? We considered counting the keys on the keyboard and taking the logarithm of that number to get the entropy of a single character, but that would be a bit of a stretch,” the team wrote in their paper.
“The English language contains ordered internal structures that make the stream of characters highly predictable. In fact, the entropy of the English language is only ∼1 bit per character. Expert typists rely on all this redundancy to type faster: If they were forced to type a random sequence of characters, their speed would drop sharply.”
Based on this, they were able to calculate that the speed of thought that a typist is working with when typing a random sequence of characters is about… 10 bits per second. Looking at other tasks—from playing Tetris to solving a Rubik’s Cube under controlled conditions to listening to English—the team estimated that most of these tasks are performed at a similarly, surprisingly low speed.
“That’s an extremely low number,” says Markus Meister, a co-author of the paper. “At any given moment, we extract only 10 bits of the trillions that our senses take in, and we use them to perceive the world around us and make decisions. This raises a paradox: what does the brain do to filter all this information?”
While our brains are dealing with the avalanche of sensory data, our conscious thoughts seem to operate at a much slower speed. The team notes that this could have implications for, for example, the creation of brain-computer interfaces. While brain-computer interfaces may one day emerge that can speed up human brain activity, we may be limited by the speed of our own cognitive capacity.
More generally, this raises a number of questions, such as why our nervous system can process thousands of elements in parallel, while our conscious thought moves at such a slow pace.
“How can humans cope with only 10 bits/sec? The intuitive answer here is that cognition at such a slow rate is sufficient for survival,” the team writes. “More precisely, our ancestors chose an ecological niche in which the world was slow enough to make survival possible. In fact, the 10 bits/sec are only needed in the worst-case scenarios, and most of the time our environment changes at a much slower rate.”
While it’s an interesting estimate of the speed of information in human thought, the team emphasizes that it raises more of a question and, rather than providing answers, offering an opportunity for further research in the future.
“In particular, our peripheral nervous system is capable of absorbing information from the environment at a much higher rate, on the order of gigabits/sec,” the team writes. “This defines a paradox: the vast gap between the tiny information throughput of human behavior and the vast information inputs on which that behavior is based. This enormous ratio—about 100,000,000—remains largely unexplained.”
Illustrative Photo by Pixabay: https://www.pexels.com/photo/light-trails-on-highway-at-night-315938/
