“…Consider next the simple act of smiling,
something we all do every day in social situations. You see a good friend and
you grin. But what happens when that friend aims a camera at your face and asks
you to smile on command? Instead of a natural expression, you produce a hideous
grimace. Paradoxically, an act that you perform effortlessly dozens of times
each day becomes extraordinarily difficult to perform when someone simply asks
you to do it. You might think it’s because if you walk over to any mirror and
try smiling, I assure you that the same grimace will appear.
The reason these two kinds of smiles differ is
that different brain regions handle them, and only one of them contains a
specialized “smile circuit.” A spontaneous smile is produced by the basal
ganglia, clusters of cells found between the brain’s higher cortex (where
thinking and planning take place) and the evolutionary older thalamus. When you
encounter a friendly face, the visual message from that face eventually reaches
the brain’s emotional center or limbic system and is subsequently relayed to
the basal ganglia, which orchestrate the sequences of facial muscle activity
needed for producing a natural smile. When this circuit is activated, your
smile is genuine. The entire cascade of events, once set in motion, happens in
a fraction of a second without the thinking parts of your cortex ever being
involved…”
Phantoms in the Brain, p. 13
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