In a review of Antonio Damasio’s new book, Natural Intelligence and the Logic of Consciousness, David Eagleman writes:

The part of the mind that Damasio says has been too long underappreciated is the feeling mind, built on interoception, which includes the continuous monitoring of respiration, temperature, heartbeat, blood circulation, blood chemistry, visceral musculature and other internal affairs.

These three categories [the perceptual mind, the reflective/linguistic mind, and the feeling mind], he explains, have different biological foundations, different evolutionary ages and different consequences. But they collaborate. We might think of an integrated mind like a smartphone: Perception and reflection are the flashy, battery-draining apps, while the feeling mind is the unnoticed and massive operating system that keeps the hardware working.

The feeling mind is the center of gravity in this book. It evolved to “continuously qualify” everything happening in the rest of the mind, assigning positive, neutral or negative valences.

To illustrate what is special about the homeostatic functions of the body, Damasio turns to often overlooked details of the neuroanatomy. The nerves carrying sight and sound are thickly myelinated (rather like the insulation on copper wiring), but he notes that the neurons monitoring your body’s interior are mostly bare.

As a result, chemical signals in the bloodstream wash directly against the nerves, producing not just digital information but qualitative events, such as pain, nausea, hunger and relief. Damasio calls the low-grade hum of this traffic the “feelings of existence”: the ineffable sense of occupying a body, which he suggests is the bedrock of subjective experience. [Continue reading…]

That the reviewer, a neuroscientist himself, chooses a smartphone as an analogy for the integrated mind, speaks to the degree to which most people have externalized their own existence inside their devices — devices we clutch as though they are life-support systems.