The enduring mystery of how a brain becomes a mind

Gottfried Wilhelm Leibniz, best known for his discovery of calculus and ensuing mathematical feud with Isaac Newton, supported Descartes’s view on the separation of the brain and the mind. He invited you to imagine yourself shrunk to the size of a flea, and then to join him on a tour of the brain at this tiny scale. (In fact, a flea would be a bit too large to properly explore the nooks and crannies of the brain, but let’s go with it.) As you wander around, there would be no indication of thoughts within the fleshy material, no ideas bubbling away inside all the biological machinery. No, he argued, the mind must be something separate, something distinct from the brain.

With the arrival of 20th-century science, Descartes’s dualism came under sustained attack. Advances in technology and biological understanding began to explore the physical workings of the brain, attempting to identify consciousness and thought in action. Researchers discovered that chemical imbalances across certain cells in the brain, known as neurons, trigger tiny bursts of electrical current. Each neuron is small and relatively simple, yet it processes signals from other neurons and, when it fires, transmits a signal to others. It was confirmed that the secret to the mind lies in electricity, and the living, active brain is awash with these bursts of electricity across its complex network of neurons.

Real-time mapping of signals coursing through the neurons revealed that Leibniz’s flea might not see any thoughts because thoughts seem to be invisible to the naked eye. The brain pulses and bursts with electrical activity, with different regions lighting up in response to various stimuli. The information relayed to your brain from your optic nerve is processed in a region at the back of your brain, where the images you perceive as the world around you are created. Smell, taste, and touch are also processed in specific regions, with the front of the brain, the cortex, thought to be responsible for thought. The mind, it seems, is purely physical — but it is built on complexity.

The physical brain

The brain’s highly convoluted network comprises over 80 billion neurons and countless interconnections. Signals trigger new signals that flow throughout the network, with electrical activity surging and cycling, building up and fading away. While it’s tempting to believe that the mind is simply chaotic electrical signals, the mystery about how the mind operates persists: How do thoughts, memories, creativity, and insight emerge from the electrical activity between your ears? Although scientists can map the electrical activity as it travels through the neurons, it remains unclear how this activity connects to the various aspects of the mind. Scientists can make an educated guess at what your brain is contemplating from the patterns of its electrical signals, but they can’t discern your actual thoughts.

So, just where is thought? And where are the complex facets of the human mind that make you … well, you? Where is love? Where are creativity and imagination? Where are memories stored? Why can I remember the lyrics of songs I haven’t heard in years but forget where I’ve put my car keys when I get home? Where are the words in my head before I type them on my laptop? How are those words translated into the keystrokes of my fingers?

The brain’s workings remain an unsolved puzzle. Even the man with one of the greatest minds of all time, Albert Einstein, was remarkable for being unremarkable. His brain was perhaps a little larger than the average, but many non-Einstein individuals have had larger brains. In terms of structure, folds and number of neurons, Einstein’s brain was essentially indistinguishable from anyone else’s. Where did those incredible insights into the nature of reality come from? And why didn’t they emerge in someone else’s head? Intelligence, like consciousness, doesn’t seem to be etched into the brain’s structure.

Is complexity the answer?

The idea that the mind is somewhat distinct from the brain remains quite prevalent today, but the emphasis has shifted to the intricacy of the neural networks within our heads. Perhaps consciousness and thought emerge as a result of this complexity — that is, they are an “emergent phenomenon” that can’t be explained simply by investigating the network. Complex networks can demonstrate remarkably strange and convoluted behaviors, and we are only now beginning to truly understand the complexity of the outcomes that arise when networks of simple processes are interconnected.

Emergent phenomena in complex networks have often baffled people. A well-known but probably apocryphal story recounts an aide from the Soviet Union visiting London in the 1980s, seeking to understand who organized bread production in the city. In the Soviet system, bread production was centralized, with every step — from flour distribution to baking to shipping to stores — tightly controlled by the government. This strict planning allowed each step to be scrutinized from above and adjusted to ensure maximum efficiency and a steady flow of bread to the people. However, in cities like Moscow, long lines at bread shops formed due to the fragility of the system, with inefficiencies creeping in and coming to dominate.

In London, there was no “bread tsar” overseeing production; the efficient system emerged from many workers performing their own tasks without necessarily considering the details of the bread appearing on the shop shelves. The millers ground the flour, the bakers baked the bread, and a distribution network of trucks and trains transported the materials. Each stage was governed by supply and demand, a local dialogue between two parties. From these countless individual decisions, a self-organizing and resilient system emerged, ensuring that bread reliably appeared on shop shelves without any central oversight.

The brain’s workings remain an unsolved puzzle.

The situation is reminiscent of the complexity found in a nest of ants. If you observe one, you’ll see thousands of individual ants scurrying about, seemingly with purpose. However, there is no single ant controlling the colony’s behavior — there is no “ant tsar!” Instead, complex emergent phenomena arise from each ant following a simple set of rules. Ants searching for food can forage about, but once they locate a food source, they head back to the nest, leaving a trail of pheromones. Other foraging ants that encounter this trail will follow it to the food source and then bring what they can back to the nest. As they do this, they reinforce the trail with their own pheromones. More and more ants raid the food until the source is depleted. If there is no stream of ants returning to lay down more pheromones, the trail evaporates and the ants go hunting for a new food source.

From the outside, this might seem like complicated behavior, but each ant is following a straightforward set of instructions. Much of what occurs in the nest appears as emergent phenomena — from the rush of soldier ants defending the colony to the tending of the queen, her eggs and the larvae. Simple ideas in the simple heads of the ants.

Emergent phenomena can be observed throughout the physical world. Water is merely a collection of molecules, each composed of an oxygen atom and two hydrogen atoms, attracting and repelling through electromagnetism. Yet a body of water can flow and bubble with turbulent eddies and swirls — emergent behavior arising from simple rules. The physical properties of matter and gases also emerge from basic principles, as water crystallizes into ice or boils off as steam; this has led some to ponder whether these principles have arisen from more fundamental phenomena.

Perhaps gravity emerges from truly fundamental aspects of space and time in the same way that the properties of water emerge from the interactions of molecules? Could it be that the reality you experience is simply the result of complex wiring? Some find this conclusion unsettling, while others see great hope in it.

This article is featured on Big Think.