Hope it's ok if I chime in on this, because I think that evolutionary psychology can help to answer your question.
Human society has evolved based upon a system of reciprocity - if you provide for me and/or my offspring, thus ensuring the survival of my genes, I will extend the same to you. Usually, it is mutually beneficial to "do unto others as you would have them do unto you." Yes, there is some cost to you (resources, time, etc., which could put the other person's genes at a relative advantage), but usually the person reciprocates, thus benefiting you and your genes. Great!
(See also
The Selfish Gene, by Richard Dawkins.)
But there are "cheaters" in the system, too - people who will gladly accept your kindness, but offer none in return. We call them "takers, not givers," "fair-weather friends," and other non-flattering names. Taken to the extreme, we call them "predators" - people who will literally destroy you because it is somehow beneficial to them. (See David Buss's excellent book,
The Murderer Next Door, and
A Natural History of Rape - a fascinating, controversial book by Thornhill, Palmer, & Wilson.)
Fortunately, we have also evolved tools for cheater-detection, which is where your "hinky meter" comes in. When you talk about the hinky meter going off, what you are really saying is, "I sense that this person is not trustworthy." You believe he doesn't play by the rules - that he is a cheater, in other words. I believe that this is largely based upon your ability to perceive and interpret the individual's behavior (verbal and nonverbal). A great example of this can be found in the work of
Paul Ekman, which was recently glamorized in the TV show
Lie to Me. This is an important skill for any social species, because we don't want to give away our resources - compromise our fitness - to someone who has no intention of "doing right by us" in return.
In this post, especially in the 1st paragraph, I have used active verbs. This is conventional, but sometimes misleading to those who aren't used to reading about evolutionary psychology. I am not say, nor do I believe, that we only do nice things for others because we want them to help us reproduce! I am saying that that is the evolutionary, biological basis for reciprocity. (And you are free to disagree with this if you wish, of course!) And I am not saying that we
consciously pick up on behavioral signals that tell us whether or not to trust a person because we are
consciously only interested in being around/helping those who can increase our fitness. In fact, as you know based on your own experience with intuition or hunches, a lot of this perception and processing is done very subconsciously. And it makes sense - the parts of the brain that apparently pick up on these cues are phylogenetically older than the cerebral cortex. Much of what they do never reaches close to the level of consciousness. But if these areas in the brain are compromised, serious deficits result. (See also Donald Pfaff's book,
The Neuroscience of Fair Play.)
http://www.amazon.com/s/ref=nb_sb_s...rds=the+selfish+gene&sprefix=the+selfish+gene
Amazon.com: The Murderer Next Door: Why the Mind Is Designed to Kill (9781594200434): David M. Buss: Books
Amazon.com: A Natural History of Rape: Biological Bases of Sexual Coercion (9780262201254): Randy Thornhill, Craig T. Palmer, Margo I. Wilson: Books
Amazon.com: The Neuroscience of Fair Play: Why We (Usually) Follow the Golden Rule (9781932594270): Donald W. Pfaff, Edward O. Wilson: Books