A new study finds an afternoon of tough thinking can also make people feel worn out as well. Researchers in France have uncovered why and how this occurs.
The research team explains that when a brain performs intense cognitive work for several hours or longer, potentially toxic byproducts build up in the prefrontal cortex. When that happens, it influences how people make decisions; directing us toward low-cost actions that require no effort or waiting as cognitive fatigue takes hold.
The findings show that cognitive work results in a proper functional alteration—accumulation of noxious substances—so fatigue would indeed be a signal that makes us stop working but for a different purpose: to preserve the integrity of brain functioning.