Twitter made it simpler again to express yourself by constraining expression to 140 characters that can in fact be generated for you through share buttons on other sites.

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Taken together, the two studies seem to indicate a direct relationship between ability to express emotion through facial expression, and the ability to experience emotion oneself, or identify it in others.

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Because each of tonight's honorees has felt the need to express themselves and share that expression with the world.

WHITEHOUSE: Kennedy Center Honorees at The White House 2011

It makes it easier for activists to express themselves, and harder for that expression to have any impact.

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The Expression of the Emotions in Man and Animals posited the theory that animals express emotion in a similar way to humans.

BBC: Friday 11 September: Darwin special