Human consciousness is a mystery that has occupied great thinkers for centuries, from philosophers who have puzzled over the nature of the mind to biologists trying to figure out how a network of neurons can work together to create self-awareness. On one hand, consciousness is a basic trait we all have in common; but, on the other, it’s abstract, transparent, undefinable, and—worst of all, from a scientific point of view—unquantifiable. That makes it very hard to study.
Now that may be changing. Over the last few years, Giulio Tononi, an eminent neurobiologist at the University of Wisconsin, has been working on a way to quantify consciousness. He argues that it’s possible to define consciousness mathematically. More than that, he says, it’s possible to measure it. Measuring consciousness—assigning a number to your current state of awareness—might sound impossible. But, using a combination of information theory and neuroscience, Tononi has come up with a plausible way to gauge how much consciousness is unfolding inside a brain at any given time. He’s already taken some rough measurements of people who are awake, sleeping, and even in vegetative or “locked-in” states.