Always great reading Michael Graziano as he wrestles with the nature and mechanics of consciousness. In an Atlantic piece, the Princeton psychologist traces the emergence of consciousness hundreds of millions of years to a process known as “selective signal enhancement,” a primitive system not even requiring a central brain, and then marches forward explaining its development from that point. 

Graziano asserts that the brain is more a prioritizing machine that edits out what’s unnecessary rather than one that needs to be in possession of all information at every moment. “The brain has no need to know those details,” he writes. “The attention schema is therefore strategically vague.”

The opening:

Ever since Charles Darwin published On the Origin of Species in 1859, evolution has been the grand unifying theory of biology. Yet one of our most important biological traits, consciousness, is rarely studied in the context of evolution. Theories of consciousness come from religion, from philosophy, from cognitive science, but not so much from evolutionary biology. Maybe that’s why so few theories have been able to tackle basic questions such as: What is the adaptive value of consciousness? When did it evolve and what animals have it?

The Attention Schema Theory (AST), developed over the past five years, may be able to answer those questions. The theory suggests that consciousness arises as a solution to one of the most fundamental problems facing any nervous system: Too much information constantly flows in to be fully processed. The brain evolved increasingly sophisticated mechanisms for deeply processing a few select signals at the expense of others, and in the AST, consciousness is the ultimate result of that evolutionary sequence. If the theory is right—and that has yet to be determined—then consciousness evolved gradually over the past half billion years and is present in a range of vertebrate species.

Even before the evolution of a central brain, nervous systems took advantage of a simple computing trick: competition. Neurons act like candidates in an election, each one shouting and trying to suppress its fellows. At any moment only a few neurons win that intense competition, their signals rising up above the noise and impacting the animal’s behavior. This process is called selective signal enhancement, and without it, a nervous system can do almost nothing.•