“Unlocking Perception: How the Concept of Zero Shapes Our Understanding of Absence” | Aeon Essays

When I go birdwatching, there’s a moment that happens often. Someone will point to a tree and ask if I can see a bird hiding among the leaves. I use my binoculars, but despite everyone’s hopes, I often only see empty branches. This experience of absence is interesting and puzzling. How does our brain perceive something when there’s actually nothing to see?

This question fascinates neuroscientists, especially those studying consciousness. Understanding how the brain handles ‘nothing’ can be tricky, but there are clearer examples of absence that can help shed light on this topic. This is why, during my PhD, I focused on how we understand the number zero.

Zero has played a vital role in human history. It struggled to find acceptance in societies that feared nothingness but thrived in others that welcomed it. This makes it more than just a number; zero is closely linked to our perception of absence. If my brain can recognize a tree full of owls, how does it know when there are no owls to count?

The mystery of zero connects deeply with how we perceive absence. When we recognize zero, our brain might be using basic mechanisms that help us understand when something is visible or not. Exploring zero could provide a new angle to investigate consciousness itself.

Zero first appeared 5,000 years ago in Mesopotamia, thanks to the Sumerians. They created a revolutionary numbering system. Instead of inventing new symbols for higher numbers, they used the position of existing symbols to determine their value. For example, in the number 407, the position of the ‘4’ signifies 400, while in 47, it means 40. This simple change made it easier to record large numbers and calculate quickly.

As numbers grew, a problem emerged: what to indicate when a column had no value? Enter zero. The Sumerians placed a diagonal wedge in empty columns to show ‘nothing is here.’ Even with this innovative approach, not everyone embraced zero. In ancient Greece, it was largely ignored, and many scholars refused to accept the idea of nothingness. They favored geometry, which did not naturally fit the concept of nothing. Some, like Aristotle, dismissed it entirely, asserting that nothingness couldn’t exist.

Despite this resistance, zero found its way to the working class, who needed it for trade and bookkeeping. This allowed zero to flourish and evolve as it moved from Babylon to India around the 3rd century BCE. In India, the notion of nothingness was part of the culture, which embraced various terms for ‘nothing’ in different contexts. Indian mathematicians like Brahmagupta established rules for zero, treating it as an important number, not just a placeholder.

By 876, zero was represented as a hollow circle in Gwalior, India. As trade routes expanded, the advanced concept of zero made its way back to the Middle East and eventually influenced Europe, notably through the work of Fibonacci in 1202. However, zero still faced skepticism; many viewed it as a challenge to religious beliefs about creation from nothing.

Over time, the practical application of zero in bookkeeping made it indispensable. By the 15th century, zero was widely recognized in European mathematics. In the late 17th century, figures like Leibniz and Newton relied on zero to develop calculus, changing how we understand mathematics and the universe.

Interestingly, children take longer to understand zero compared to other numbers. While they easily grasp quantities like two or three toys, zero is abstract and represents nothing. They might wonder how one even counts zero fish! Research shows that even young infants can track numbers up to a point, but struggle with zero. For example, when presented with puppets, they expect to see a number greater than zero and react differently when the count drops to zero.

As children grow, they gradually understand the meaning of zero, but misconceptions remain. Many preschoolers think one is the smallest number and sometimes get confused when comparing zero to other numbers. Studies also show that they can perform better if they think of ‘nothing’ rather than zero, revealing a strong link between zero and absence.

Given this connection, how is zero represented in our brains? Recent studies show that certain neurons respond specifically to zero and empty sets in primates and humans. Researchers have discovered that some neurons fire more when they see no dots than when they see any other number. These ‘zero neurons’ help distinguish between presence and absence in our perception.

By examining how our brains process zero, scientists hope to better understand how we perceive absences or nothingness. The mechanisms that represent zero in our brain can also apply to our awareness of missing information.

Experiments show that detecting absence isn’t straightforward. Our brains are wired to notice the presence of objects, and this affects how we perceive nothingness. This leads to the idea that our cognitive processes actively recognize when something is not there. For instance, when showing people partially hidden letters, they sometimes decide there’s more out there, even if there’s not. This reflects a deeper understanding of how our brain monitors its own ability to perceive.

So, what does this all mean? The mechanisms that help us perceive zero might relate to how we understand all forms of absence. This is fascinating because it suggests that recognizing zero could not only reflect mathematical ability but might also indicate a deeper awareness of consciousness itself. Just as zero unlocked the door to mathematics, studying it further might help unravel some of the mysteries of our own minds.

In the end, while I might not always see the birds I hope for, I now have a richer understanding of what it means to see nothing. That complexity adds meaning to my birdwatching experiences, reminding me that nothing really can matter.