Researchers Reveal How Our Brain Analyzes Zero as a Numeral or Nothing

Zero is a number that holds a unique place in mathematics and our daily lives. From balancing your checkbook to advanced computer coding, zero plays a pivotal role. But have you ever stopped to think about how your brain perceives this elusive concept of “nothing”? It turns out, scientists have been trying to unravel that very question, and recent research has shed new light on how our brain’s neurons understand zero as a symbol and as the absence of anything.

Researchers from the University of Bonn and the University of Tübingen published an intriguing study in Current Biology, exploring how single neurons in the human brain represent zero. Specifically, they wanted to know how our brains handle zero when it appears as an empty set (like seeing no items) or as the symbolic numeral “0.” Their findings provide a fascinating glimpse into how the human mind processes this special number, suggesting that neurons treat zero as both distinct from and integrated with other numbers on the number line.

For this study, the researchers recorded the activity of individual neurons in the medial temporal lobe (MTL) of patients undergoing neurosurgery. The researchers asked the patients to perform tasks that involved both symbolic numbers, such as 0–9 in Arabic numerals, and nonsymbolic quantities, such as dot patterns, where the absence of dots represented zero. The researchers discovered that different neurons in the MTL responded specifically to zero when it appeared in either symbolic form or as an empty set.

Esther F. Kutter, one of the lead authors of the study, explains the significance of this finding: “What we observed is that neurons selectively respond to zero, both as a symbolic number and in its nonsymbolic form, but interestingly, they do so in different ways. This suggests that the brain recognizes the abstract concept of zero while also integrating it with other numbers.”

Why Is This Important?

Understanding how our brain processes numbers, especially zero, has implications that stretch far beyond the world of mathematics. Numbers are foundational to many aspects of our cognitive development, and zero is a particularly complex concept to grasp. The idea of “nothing” might seem straightforward, but historically, zero was a latecomer in the development of number systems. In fact, mathematical notation didn’t widely accept zero until the seventh century.

Neuroscientist Andreas Nieder, another senior author of the study, explains: “Zero holds a special status because it’s not just a number; it’s a symbol for the absence of something. From a young age, children struggle with this concept because it’s not inherently intuitive. Our study shows that the brain’s neurons help us make sense of zero by integrating it into the number line, so we eventually come to see it as a number like any other.”

How Our Brain Treats Zero

One of the most striking findings from this research was that neurons in the brain responded to zero with something called a “numerical distance effect.” This means that the brain treats zero as being close to small, positive numbers, like one and two on a mental number line. Neurons that fired in response to the symbolic numeral zero would gradually reduce their activity as they encountered larger numbers. This suggests that the brain considers zero part of the broader numerical spectrum rather than some isolated, abstract concept.

However, the researchers also discovered that neurons coded for zero differently depending on whether it appeared as a symbol or an empty set. When participants viewed dot patterns representing “nothing” (i.e., an empty set), the brain treated it as a distinct category separate from small numbers like one or two. On the other hand, the brain seamlessly incorporated the numeral zero into the number line, just like it would any other number.

This dual processing shows how flexible and adaptive our brain is. Although we can understand zero as a “nothing” category, our brain quickly contextualizes it as part of the numeric system.

This study opens up new avenues of research into how humans and other animals understand numbers. Previous studies have shown that even monkeys and birds have some basic understanding of the absence of items, suggesting that the ability to perceive “nothingness” might have deep evolutionary roots. By pinpointing specific neurons responsible for processing zero in humans, scientists can now explore how this ability evolved and how it differs across species.

Moreover, understanding how the brain processes abstract numbers like zero could have important applications in artificial intelligence (AI). Deep learning systems, modeled after the human brain, are already beginning to show spontaneous recognition of numerosity, including zero. Insights from neuroscience studies like this one could help improve the way AI systems understand and manipulate numbers, potentially leading to advances in fields like autonomous decision-making and robotics.

While zero may not seem like a big deal in our day-to-day lives, its role in human cognition is profound. As this research shows, our brain’s ability to handle zero isn’t just about understanding the concept of nothingness. Instead, our mental number line integrates zero, guiding us through everything from basic counting tasks to intricate mathematical theories.

As Florian Mormann, one of the senior authors of the paper, puts it, “Zero might seem like nothing, but for the brain, it’s everything. It’s a powerful tool that allows us to think abstractly, organize the world around us, and develop the complex mathematical systems we rely on today.”