So essentially, one nonverbal sign (one smile, one play of the hair, one sarcastic eye roll) essentially means nothing. In the grand scheme of human interaction we throw out tons of nonverbals every single day. So one of the most important things you need to do is not just look for one nonverbal behavior. You need to look for clusters of behavior. So the more behaviors the better. Usually when somebody's mad, it's not just a frown. There's more behaviors: they have closed posture or their eye contact decreases significantly. There's always clusters.
So it's very very important that you look to cluster behavior. You can't focus on one thing. Usually you want to see 3-5 clusters of behaviors. So 3-5 separate things that you can point to that indicate a feeling, an emotion or a physical state. Ideally what you want to do is see 3-5 clusters that deviate from somebody's baseline. So if somebody has a standard way of behaving and all of the sudden they act differently in 3-5 ways, 3-5 nonverbal differences, essentially. And that's going to be really really powerful in determining whether or not your're right or wrong.
Because at the end of the day, you're really just making a deduction about human behavior. You don't...you're not necessarily sure. You want as much information as possible. Essentially, you're throwing up all this information in the air and then trying to deduce what the person's feeling, what the person's thinking, what the person's acting, so one and so forth. So essentially what you're trying to do is gather more information. So one thing's not enough. Like if you're at a bar and you're across the table and the girl smiles at you, it doesn't necessarily mean anything. She could be smiling at you because you look like her brother. I mean, you don't really know why. You have to look for a lot more variables than just one.