I'm going to give you tips to predict human behavior, but it requires time and observation of specific individuals, you won't be able to generalize it, AKA you'll have to do the "process" again and again for each person.
1) If you do, stop thinking people lie unless you have objective evidence to argument it (AKA you SAW someone doing something they said they wouldn't). Otherwise, believe what people say and do, and do not assume why people do it, just observe and be objective (i'll explain in a moment why this is important)
2) Generalize the next "concepts" as if they were REALLY similar or the same: Idea, belief, value, thought, feeling (maybe), and other similar concepts.
3) Pay attention to what the person you're interested in says in relation to how he or she perceives the world (reality) and values it, for example, what he/she considers bad or good, basically their morality. The more "morality" you understand of the person and "ideas" or "values" the broader your results will be.
4) OBSERVE THEM objectively, this is SUPER HELPFUL, observe them in different situations, in different moments, basically pay attention to what they do when you interact with them and in other ocassions when you can just watch them, how they react, how they respond to whatever, that's what you want to know
When you gather a lot of information about this, you will be able to predict a person behavior, even their ideas, when something happens, because you'll be aware of how they react behaviorally and morally to the situations you analyzed (that's why the more you observe, the better you'll be to predict them)
I'm a psychologist in the process of getting a master lol, what i just told you are some of the condensed principals psychologists use to understand and predict human behavior. So use it wisely. Studying psychology will actually help you to do so, but you need good psychology, like Cognitive-behaviorism, or radical behaviorism, anything else other than that is BS.