10 bits per second

A bit is a basic unit of information in computing. A typical Wi-Fi connection, for example, can process 50 million bits per second. Humans think at a speed of 10 bits per second.

This is an extremely low number, 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. This raises a paradox: What is the brain doing to filter all of this information?

There are over 85 billion neurons in the brain, with one third of these dedicated to high-level thinking and located in the cortex. Individual neurons are powerful information processors and can easily transmit more than 10 bits per second of information. But why don't they? And why do we have so many if we're thinking so slowly?

Another conundrum that the new study raises is: Why does the brain process one thought at a time rather than many in parallel the way our sensory systems do? For example, a chess player envisioning a set of future moves can only explore one possible sequence at a time rather than several at once. Perhaps this is due to how our brains evolved.

The earliest creatures with a nervous system used their brains primarily for navigation, to move toward food and away from predators. If our brains evolved from these simple systems to follow paths, it would make sense that we can only follow one "path" of thought at a time. Human thinking can be seen as a form of navigation through a space of abstract concepts, how this constraint—one train of thought at a time—is encoded in the architecture of the brain.

Our ancestors have chosen an ecological niche where the world is slow enough to make survival possible, 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 new quantification of the rate of human thought may quash some science-fiction futuristic scenarios. Within the last decade, tech moguls have suggested creating a direct interface between human brains and computers in order for humans to communicate faster than the normal pace of conversation or typing. But would our brains that communicate through a neural interface still process at the same speed of 10 bits per second?