She was great because she was performing a seriously difficult mental task — simultaneously listening and translating on the spot — in a high-pressure, high-stakes situation. Sure, she was expressive, but that’s because she was speaking a visual language. Signers are animated not because they are bubbly and energetic, but because sign language uses face and body movements as part of its grammar.

In American Sign Language, certain mouth and eye movements serve as adjectival or adverbial modifiers.

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