From Chris Nunn
Randal A. Koene’s article “How to copy a brain” was a blast from the past, with its implicit assumption that neurons are all that matters when it comes to the basis of “mind”, and that associated computations are primarily digital (27 October, p 26). In fact, we now know that we should be thinking in terms of systems that include both neurons and astrocyte cells.
Humans have about twice as many astrocytes as neurons, and by comparison, C. elegans nematodes have at least five neurons per astrocyte. The principal computations are likely to be analogue.
The article asks, “What will life be like for human minds embodied in non-biological materials?” The answer is “probably nothing”, since we know even less about what underlies consciousness than we do about what is at the basis of “mind”. The road ahead will lead us into landscapes that we can only begin to envisage.
“Continuity of self could be assured, despite minds having novel embodiments,” writes Koene. Perhaps we can overcome the difficulty of capturing the state of a brain without dumping so much energy into it that we disturb it radically. We might ignore the fact that neurons die off in quite unpredictable ways not susceptible to modelling – such as when I can’t recall the name of Aunt Jemima’s cat, for example. We could set aside the issue that a brain is not a closed system, but reacts to the nutrients, hormones, alcohol and other drugs in which it is bathed.
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That leaves the issue of chaos. The brain is surely a richly interconnected system, riddled with feedbacks. It is self-modifying, reprogramming itself daily. All hope of determinism and predictability is doomed.
Still, suppose that we transcribe a brain into an emulator, and for convenience assume that the original person promptly dies. We can live contentedly with the fact that we cannot predict the emulator’s actions, for the same was true of the person.
But what if, in a moment of ill-considered mischief, we make a second copy?
If the twin emulators are truly brain-like, their thoughts, actions, decisions and characters will slowly but surely diverge. Which, then, is the true continuation of the original self?
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