How entropy and equilibrium can help explain consciousness

WHAT is consciousness? This is arguably the biggest remaining mystery of the human brain. No wonder it is known as “the hard problem”. We can’t even agree whether consciousness is one thing or a variety of different states. However, new ways of exploring that question shed some intriguing light on this most elusive of concepts.

Though we use language like “losing consciousness” for fainting or falling asleep, researchers have long understood that consciousness is more complicated than just flipping a metaphorical switch from “on” to “off”. However, there is still much debate over whether it is a single phenomenon with many continuous shades, which you might picture as a dimmer switch, or a collection of discrete states, like separate television channels.

Thinking about consciousness from the perspective of a physicist may help resolve the question. That’s because the brain constantly shifts between states defined by patterns of electrical signals, and physicists have metrics for examining such busy, ever-changing systems. In 2014, Robin Carhart-Harris at the University of California, San Francisco, and his colleagues hypothesised that entropy may be a particularly useful one.

Entropy describes how disordered a system is. One measure of entropy is how many different microscopic configurations (such as arrangements of water molecules in a glass) there are in a given macroscopic property (such as the volume of that glass). The researchers proposed that brain states with greater entropy, as measured…