My sims do not have free will, but despite this they are extremely good at showing me their personalities.
Just last week my 19 year old legacy heir has made the next heir with Siobhan Fyres. When I directed him to the bookcase the next day I let him the choice what he wanted to read and what did the young father-to-be grab? "I'll be a father", my custom pregnancy book for males!
He then got dragged outside by the family cat and somehow the cat action also pulled Siobhan. So there they stood on the lawn, Caspar still absorbed in the book and Siobhan looking over his shoulder. Suddenly she went through a "Ugh, this is disgusting" animation.