Even as they become increasingly indispensable, computers still arouse fears that they will distort our essential humanity.

Could super-intelligent robots ultimately enslave us? Will cyborgs — part-human, part-implanted electronic circuitry — acquire powers that we can only dream of, their bionic limbs animated by a mechanical soul? Could the cuddly robots programmed to trigger hard-wired nurturing responses that are now being promoted as pets or companions for the young and old redefine what it means to love? Michael Chorost is a cyborg and his highly intelligent and searingly honest story about how it feels suggests that we should not be too worried. Having had very poor hearing from birth, he became totally deaf in 2001. His hearing is now entirely controlled by a computer sending signals to a ceramic and titanium unit surgically implanted into his inner ear — the cochlea.

As his subtitle suggests, hardware is not about to replace the incredibly complex “wetware” of our brains any time soon and his “bionic” ear propelled him towards other humans, not away. His search for love in the world of online dating proved just as challenging as learning to hear electronically.

Chorost is hugely admiring of the science. Lines of computer code perform a magic that ancient wizards could only dream of; conjuring his hearing back from the dead. After a year of frustrating experimentation with the implant, he gained about 80 per cent of the hearing of a normal person. That is all the more remarkable considering how crude the implant is compared to the real thing; in the cochlea there are 3,500 hair cells, each responsive to different aspects of sound; the implant has just

16 electrodes directly stimulating the auditory nerve, even though it does update that input 32 million times a second. In place of three different systems for modifying the input, there is just one.

You might think it just a matter of time before the hardware catches up but this is where it gets interesting. Even when a computer is delivering data to the brain, you cannot sidestep emotions. To his amazement, Chorost found that feelings and belief affected how much of a conversation he understood. And it gets more unpredictable; sometimes the meaning didn’t come through, no matter how involved he was. The workings of bionic implants are still far from robotic.

However, while his mental state was modifying the input, simultaneously the processors in the implant were physically reshaping his brain. The patterns of data arriving in the auditory cortex are unlike those generated by a normal ear so new connections grew between the neurons and his brain rewired itself to handle them.

This had a bizarre effect. Early on, at times all he could consciously hear of a conversation was auditory mush. Yet phrases and sentences would then float into his mind; his brain was processing data and turning it into meaning at an unconscious level, just as it would normally. What were missing were the smoothing processes that give the rest of us the illusion that that is no gap between hearing and understanding.

His bionic ear also stripped away another illusion, making him a living embodiment of the insight of the Enlightenment philosopher David Hume that we can never know anything about the real nature of the external world; all we know is the data that flows in from our senses. The rest of us perceive the world so seamlessly that it is hard to accept this emotionally, let alone to appreciate its implications.

Chorost experienced daily the arbitrary nature of sensory information. He could switch between two different programs, each processing sounds in different ways. By tweaking various parameters, he could theoretically have 230,000 versions of a sound. So which was the “real” one? A cyborg, he concluded, must view the world from multiple perspectives, making him a thorough-going relativist. The notion that any one ideology had a monopoly on “truth” became absurd; each of us constructs our own world.

But Rebuilt is more than just a philosophical exploration of cyborg reality; the narrative drive comes from its human dimension, as Chorost attempts, often painfully unsuccessfully, to find a girlfriend: being deaf from birth combined with a love of computers is no recipe for sexual success.

Aside from emphasising the biological side of the cyborg, his dating disasters highlight what really distinguishes humans from computers — the web of social connections in which we are embedded. Chorost’s body had become a battleground between the “hyper rational structures of technology” and the “warmth of human community”.

But the human won out as he realised that what really mattered was upgrading himself, not his software. His own psychological changes allowed him to make contact with people more deeply and intimately. If all cyborgs are as reflective and compassionate as Chorost we’ll be fine.

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