One of the running themes of Natural-Born Cyborgs is that our sense of ourselves is rather more malleable than we think: the connection between our brains and bodies is at once intimate and contingent. Indeed, after a couple introductory chapters that are principally concerned with surveys of work in ubiquitous computing, tangible computing, wearable computing, and augmented reality, the book turns to consider the way our minds and memories work; the way our sense of our bodies in constructed; and our relationships to the space around us. After the lab tours, it’s more than a slight change of ground, and one must be prepared for it.

The long and short of all three chapters is that while we have stable senses of the world around us, and believe that our bodies have clear boundaries that separate “us” from that world, the truth is more complex. The information we gather about the world is opportunistic, and pretty much created on the fly. For example, we retain far less visual information about our surroundings than we expect; our focus is pretty narrowly confined most of the time, and if we need to check on something at the periphery of our vision, we refresh that information (look over for an instant), rather than try to recall it.

Further, you can pretty radically alter the ways we perceive the world, and our brains eventually can readjust. There are famous experiments in which people are made to wear glasses that turn the world upside-down; after a couple weeks, something switches in the brain, and the wearers stop noticing the effect. What’s particularly interesting about this is that experiments with manipulating vision show that people can adapt to new systems– but not if they don’t act them out.

A subject fitted with the [reversing] lenses, but simply pushed around in a wheelchair, does not show the adaptation, while one who walks along a complex trail does.

So we can construct and reconstruct our perceptions of the world, though it’s a project that requires active engagement, rather than passive observation:

The whole business of seeing and perceiving our world is bound up with the business of acting upon, and intervening in, our world. (95)

Indeed, the “passive” observation turns out to be as much an oxymoron as “jumbo shrimp.”

Why is this so important? Clark is on the lookout for the seams between our brains and bodies, those points where are perceptions are actively constructed, because they’re places where we can graft technologies onto our selves, or insert them in the brain-body-world loop. This is the neurological and psychological foundation for the claim that our ability to be cyborgs is what makes us human: it turns out to be a consequence of the way the relationship between our brains and bodies is constructed. We’re natural born cyborgs, indeed.