Nowhere to hide
Facial recognition is not just another technology. It will change society.
THE human face is a remarkable piece of work.
The astonishing variety of facial features helps people recognise each other and is crucial to the formation of complex societies.
So is the face's ability to send emotional signals, whether through an involuntary blush or the artifice of a false smile.
People spend much of their waking lives, in the office and the courtroom as well as the bar and the bedroom, reading faces, for signs of attraction, hostility, trust and deceit.
They also spend plenty of time trying to dissimulate.
Technology is rapidly catching up with the human ability to read faces.
In America facial recognition is used by churches to track worshippers' attendance; in Britain, by retailers to spot past shoplifters.
This year Welsh police used it to arrest a suspect outside a football game.
In China it verifies the identities of ride-hailing drivers, permits tourists to enter attractions and lets people pay for things with a smile.
Apple's new iPhone is expected to use it to unlock the homescreen.
Set against human skills, such applications might seem incremental.
Some breakthroughs, such as flight or the internet, obviously transform human abilities; facial recognition seems merely to encode them.
Although faces are peculiar to individuals, they are also public, so technology does not, at first sight, intrude on something that is private.
And yet the ability to record, store and analyse images of faces cheaply, quickly and on a vast scale promises one day to bring about fundamental changes to notions of privacy, fairness and trust.