Why Is the Human Brain So Efficient?


The brain is complex; in humans it consists of about 100 billion neurons, making on the order of 100 trillion connections. It is often compared with another complex system that has enormous problem-solving power: the digital computer. Both the brain and the computer contain a large number of elementary units—neurons and transistors, respectively—that are wired into complex circuits to process information conveyed by electrical signals. At a global level, the architectures of the brain and the computer resemble each other, consisting of largely separate circuits for input, output, central processing, and memory.

Liqun Luo | NAUTILUS

Which has more problem-solving power—the brain or the computer? Given the rapid advances in computer technology in the past decades, you might think that the computer has the edge. Indeed, computers have been built and programmed to defeat human masters in complex games, such as chess in the 1990s and recently Go, as well as encyclopedic knowledge contests, such as the TV show Jeopardy! As of this writing, however, humans triumph over computers in numerous real-world tasks—ranging from identifying a bicycle or a particular pedestrian on a crowded city street to reaching for a cup of tea and moving it smoothly to one’s lips—let alone conceptualization and creativity.

So why is the computer good at certain tasks whereas the brain is better at others? Comparing the computer and the brain has been instructive to both computer engineers and neuroscientists. This comparison started at the dawn of the modern computer era, in a small but profound book entitled The Computer and the Brain, by John von Neumann, a polymath who in the 1940s pioneered the design of a computer architecture that is still the basis of most modern computers today.2 Let’s look at some of these comparisons in numbers (Table 1).

The computer has huge advantages over the brain in the speed of basic operations.3 Personal computers nowadays can perform elementary arithmetic operations, such as addition, at a speed of 10 billion operations per second. We can estimate the speed of elementary operations in the brain by the elementary processes through which neurons transmit information and communicate with each other. For example, neurons “fire” action potentials—spikes of electrical signals initiated near the neuronal cell bodies and transmitted down their long extensions called axons, which link with their downstream partner neurons. Information is encoded in the frequency and timing of these spikes. The highest frequency of neuronal firing is about 1,000 spikes per second.

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