Yes, I can smile, however, I'm not great at intentional smiles and thinking of something nice doesn't necessarily trigger a smile when needed (for example for a photo, especially not if it is made in a hurry).
In another thread featuring this topic, I compared it to the Terminator in Terminator 2 trying to make his first smile. That's how it feels like to me when I try to force it.
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Diagnosed with Aspergers.
BSP-errors are awesome.