I meant that their facial expression, look in their eyes, etc. is an unconscious (and therefore harder to fake) signal of whether things are going well for them

I meant that their facial expression, look in their eyes, etc. is an unconscious (and therefore harder to fake) signal of whether things are going well for them. I didn't mean that people are happy when they intend to communicate that things are going well for them, but rather, happiness is that which leads them to unconsciously communicate it. (where by "going well for them" I mean like, "for what they care about". Someone could by in their dying moments, but receive very good news about e.g. their loved ones and their life's work, and be happy.)