What is it about the human brain that gives us these extra layers of recursion and allows us to begin to know ourselves? What is the magic ingredient?
What seems to pick primates out from the crowd is that they have unusually efficient ways of cramming more neurons into a given brain volume. In other words, although a cow and a chimpanzee might have brains of similar weight, we can expect the chimpanzee to have around twice the number of neurons. And, as our species is the proud owner of the biggest primate brain by mass, this creates an advantage when it comes to sheer number of neurons.
We do not yet know what this means for our unusual capacity for self-awareness. But, very roughly, it is likely that there is simply more processing power devoted to so-called higher-order functions—those that, like self-awareness, go above and beyond the maintenance of critical functions like homeostasis, perception, and action.
We now know that there are large swaths of cortex in the human brain that are not easy to define as being sensory or motor, and are instead traditionally labeled as association cortex—a somewhat vague term that refers to the idea that these regions help associate or link up many different inputs and outputs.