When It Comes to Thinking, Our Brains Are Surprisingly Slow

For as brilliant as the human mind can be, there are still limitations that hinder the potential of our brains. The most baffling instance of our mental shortcomings is related to how we think. Despite the brain boasting billions of neurons that dictate our every move, humans have a surprisingly constrained thought process, and scientists may now have answers to explain this mystery of human inefficiency. 

A new study recently published in the journal Neuron has quantified the speed of human thought, demonstrating an anomaly in brainpower. The study comes from the California Institute of Technology, where researchers working in the laboratory of biological sciences professor Markus Meister study neuronal circuits — in other words, groups of interconnected neurons that communicate with each other, facilitating functions of the body and mind. 

In the study, graduate student Jieyu Zheng examined scientific literature on human behaviors from reading and writing to solving Rubix cubes, crossing this analysis with knowledge of information theory — a mathematical field focusing on how information is processed, stored, and transmitted. 

The study reveals that humans think at an average speed of 10 bits per second. The curious part of this rate, though, is that the individual neurons in our brains (over 85 billion total) are technically powerful enough to process information much faster than 10 bits per second. Yet, the researchers discovered that the brain limits the speed of thought processing. 

The rate of thought processing is also much slower than our bodies’ sensory system, which acts 100 million times faster according to the researchers. The chasm between thought processing speed and sensory processing speed in humans raises many questions for neuroscientists. 

While our sensory system processes thousands of inputs simultaneously, we cannot have more than one concurrent thought going through our mind at any moment. But why is this?

Read More: How Our Brains Organize Abstract Scientific Concepts

The study suggests that our brains came to work this way through evolution. The first animals to develop nervous systems — likely during the Ediacaran period, 635 million years to 543 million years ago — would have used their brains to navigate, moving toward food or away from predators. These behaviors fit with the idea that humans simply needed to follow a single path forward, or adhere to one thought, at a time. 

Although it may seem counterintuitive, the sluggish speed of our thoughts may have arisen simply because it was enough for our ancestors to survive. Because the environment around us often changes at a rather leisurely pace, the 10-bits-per-second rate of thought processing has been suitable for decision-making throughout the centuries.

Humans are not the multitasking masters we often think we are. As one 2019 study puts it, the brain does not contain the neural “building blocks” to engage in more than one task at the same time. Instead, the brain rapidly switches between two tasks rather than actively pursuing both at once. 

Before the brain moves from one task to another, it can prepare itself and anticipate when a switch is going to occur. Task-switching can also fluctuate depending on the intensity of the tasks. Something that requires a lot of focus, for example, will render a person less ready to switch tasks. 

Switching tasks requires an associated cost that slows us down and adds more time to the completion of a task. Several experiments have demonstrated that people are slowed down when they have to switch between multiple tasks. So when we multitask, it may seem like an impressive strategy, but it usually impacts our performance in a negative way. 

Read More: What Happens in Your Brain When You Make Memories?

Zheng and Meister’s research casts doubt on ambitious technological concepts that have proposed a link between brains and computers. Knowing the limited rate of thought processing in humans, it appears that implantable brain-computer interfaces would not necessarily accelerate the brain’s rate of communication, according to the new study.

Looking forward, though, the researchers are more concerned with taking a deeper look at the mechanics of the brain to understand why it can’t handle more than one thought at a time.

Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• Neuron. The unbearable slowness of being: Why do we live at 10 bits/s?

• Caltech. Thinking Slowly: The Paradoxical Slowness of Human Behavior

• National Library of Medicine. Multicosts of Multitasking

• American Psychology Association. Multitasking: Switching costs

Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.