Smiles and laughs

I discovered that I have two types of laughs not to mention the million types of smiles. My smile can reflect sarcasm, shyness, boredom, indifference, apathy, empathy, sadness, anger, sorrow, love, likeness, cheerfulness, etc. But I only have two types of laughs and they can be discerned if you know me from the position of my neck: A true laugh where my neck leans backward and a fake laugh where my neck leans downwards. I smile more than I laugh, and I only use my fake laugh when I cannot avoid laughing because it socially seems as a necessity not to offend or hurt someone. I don't know if my neck position is a universal feature of body language but I do know that I have a quite good control over my facial muscles except for my lower lip which betrays me. Someone I know (that same one) would tell in a second what I am feeling just by looking at my lower lip. In cases of embarrassment or when I am shaking in my shoes, he would look at my lower lip and laugh (backward).