While I agree that doing your homework is a good idea for any big ticket item, there are many other ways to jack with numbers in order for corporations to make you pay more than you should. This also doesn't cover work or social interactions. It amazes me how stubborn you are when non-verbal communications is the largest component of communication between animals, including humans. And while I understand some are impaired in this area, most people aren't. So I think it's a great idea for people to do what works for them personally since there's no fascist state of behaviour.
I am well aware of those, which is why I go in with a target final price. I don't care how the salesman wants to make that up with his combination of discounts and surcharges and gimmicks. Show me the bottom line, and it is either close enough to mine, or I walk out. I read the paperwork carefully and make sure nothing changes. If it does, I walk out. I can be a very easy customer if they just give me a straight answer and make a clean deal. (Leaves them more time to bamboozle someone else.)
It amazes me how stubborn you are about insisting every human fits whatever coarse generalization you wish to believe here. I can guarantee you that the bulk of what I communicate each day can only be put across with words, possibly diagrams, occasionally actions (e.g. showing someone how to do something). Unlike you, I am not going to claim this is true for everyone, just that I not surprisingly find it easiest to communicate with people who are the same way. Fortunately I have many such people in my life. I give a work example below in my reply to Metis, and follow a similar strategy socially as well. I don't have time or energy to try to sift through everyone else's nonverbal BS. If they are willing to out and tell me something, though, I am happy to consider it.
Even if you know it's not?
How do you get from there to finding out the truth, if at all?
Sometimes you never find out the truth. That would be ideal to do so, but not the main goal which is instead to accomplish whatever needs to be done. As an example, say your coworker claims he is too busy to help you with something you have asked him to do. You suspect for whatever reason that this isn't the case and he really has plenty of time. The reality you may have to deal with is that you cannot count on his help. It is almost irrelevant if he is lying, though if this happens often, it can cause you to lose respect for him as a colleague.
On the other hand, your own perception of his workload might be in error and he really doesn't have time. One way to take what he says at face value would be to go to the boss and say, "I really need Bob's help on this as he is the only one who has experience doing X, but he told me he is too busy right now. Do you know anyone else with experience doing X?" Boss either gives you a referral, or might say, "Really? Bob just finished a big project and should have plenty of time right now. I'll have a chat with him." or: "No, Bob is the only one. I'll get Sue to take over doing A this week, which will give Bob some time to help you." Either way, Bob's excuse is now the boss' problem.
Feeling-instinct is usually at least partly based on body language. Not always. But it sounds like Coriolis either bypasses it or doesn't read it much. [MENTION=9811]Coriolis[/MENTION], do you get gut feelings at all and do they weigh in on your decisions?
I've gotten gut senses not to go to a place, take a certain action, or deal with a particular person. When I've overridden them and done it anyway, I've come to find out that they were right. Even sometimes when I have followed them, I've found out later that they were accurate. Now I try to heed them.
See, to me these are intuitions. I get them all the time, but mainly about events or decisions rather than people. I do get gut feelings about people and they can be strong but are almost always very vague. Meaning: I might feel something is off here, this person isn't on the level, but I will have no idea in what way or why, or what the "truth" of the situation would be. Pressing for answers directly almost always would do more harm than good. All I can do is proceed with caution, while taking what presents itself at face value and watching for additional evidence to surface.