Lord Byron (George Gordon Noel Byron) once said...
So well she acted all and every part
By turns--with that vivacious versatility,
Which many people take for want of heart.
They err--'tis merely what is call'd mobility,
A thing of temperament and not of art,
Though seeming so, from its supposed facility;
And false--though true; for surely they're sincerest
Who are strongly acted on by what is nearest.