In some ways people are like computers. When you make these judgments about others you are relying on past experience, reading their body language, detecting stress in their voice, eye contact, all kinds of things. These little determiners are programmed into your brain and it happens without having to think about it all, but your subconscious adds all that information up to decide whether to trust someone. If a person has had bad programming, lived through a lot of abuse, is an addict, etc. they can be using incorrect filters to process that same information. One example is women who continually seek out abusing relationships, even though there is nothing enjoyable about being abused. They are relying on faulty information, misreading the cues that other people can see clearly. So no, it doesn't work for everyone.