The earliest known writing probably emerged in southern Mesopotamia around 5,000 years ago, but for most of recorded history, reading and writing remained among the most elite human activities: the province of monarchs, priests and nobles who reserved for themselves the privilege of lasting words.

Unlike us, machines do not have a 'nature' consistent across vast reaches of time. They are, at least to begin with, whatever we set in motion - with an inbuilt tendency towards the exponential.

For all the sophistication of a world in which most of our waking hours are spent consuming or interacting with media, we have scarcely advanced in our understanding of what attention means.

The biggest neurological turn-on for people is other people. This is what really excites us. In reward terms, it's not money; it's not being given cash - that's nice - it's doing stuff with our peers, watching us, collaborating with us.

Once the words of a book appear onscreen, they are no longer simply themselves; they have become a part of something else. They now occupy the same space, not only as every other digital text, but as every other medium, too.

The really interesting stuff about virtuality is what you can measure with it. Because what you can measure in virtuality is everything. Every single thing that every single person who's ever played in a game has ever done can be measured.

For the moment, machines able to 'think' in anything approaching a human sense remain science-fiction. How we should prepare for their potential emergence, however, is a deeply unsettling question - not least because intelligent machines seem considerably more achievable than any consensus around their programming or consequences.

We are all amateur attention economists, hoarding and bartering our moments - or watching them slip away down the cracks of a thousand YouTube clips.

As a medium, electronic screens possess infinite capacities and instant interconnections, turning words into a new kind of active agent in the world.

Vast volumes of mixed media surround us, from music to games and videos. Yet almost all of our online actions still begin and end with writing: text messages, status updates, typed search queries, comments and responses, screens packed with verbal exchanges and, underpinning it all, countless billions of words.