Where does that certainty come from? How do I separate familiar faces from strange ones?
Like everyone else I probably have a few thousand faces filed away in my memory banks. There are the people I see regularly in my daily rounds. And then there are the famous people from the movies or in the magazines. I rarely see those famous people in real life, but I still recognize them at a glance from a blurry photo or from a caricature.
I can recognize all these thousands of faces at any angle, in any lighting, and with any facial expression. I unconsciously adjust my mental image of each face as each person grows older, grows a mustache, or gets a new haircut.
If I don’t see a teenager for a few years, I often don’t recognize them at all. They become, for a moment, strangers. That experience is jarring for me, and it must be a strange experience for the teenagers, too.
As we glance at the faces of people walking on a busy sidewalk in our hometown, we automatically check each face to see whether the person is an acquaintance or a stranger. Our behavior changes accordingly. We greet those we know and pass over the rest.
Aside from categorizing people according to gender, the division of people into the two sets of acquaintances and strangers must be one of the deepest unconscious tasks of visual perception.
Jules Breton once observed of his beloved Paris:
“It is a singular fact that when I am in Paris I fancy I recognize the faces of those I meet in the streets. I do not experience this feeling in any other city. This is because Paris reunites the various types one has seen elsewhere, and which strike one like old acquaintances, made one does not remember where.”
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