"I don't know"
How often have we heard this, from people who we are talking to.
Interestingly, a very true "I don't know" is only said as, most often, it starts with "Oh really....." and then goes with a good few sentences of answer. Another mode is "I don't think so", it means they gave a thought to the question and they don't agree on whats said, something like that didn't happen. Very emotionally balanced person, who honestly doesn't know the answer, but really wants to help the other says "What makes you think/say so" as gently as possible.
"I don't know" can be replaced, if honestly said, by "I don't want to answer", "I know but can't answer for saving someone else", "I know but i want to save myself from a catastrophe", "I know but not interested in gossip", "I know but it may or may not be true, so i can't say with confidence, even for a good purpose", "I know but its too late" and so on.
Its really very strange, almost 90% of the times it turns out to be false. So we can actually sense if one of the above is said, in my experience with the below cues.
There is a character to this particular sentence, as to in what velocity it is said, whether the person is able to look us in the eye when they say, more so, whether their eyes talk the same as their mouth. How quick was this response.
We will see each one...... 1. Velocity When someone says it very very fast, it really means they are angered by the question, which got this response. They might or might not know the answer to the original question, but they really are irritated even to think about the answer and respond. They either want to rudely stop the conversation further or they know the answer, but would have given it "if" asked nicely.
When it is too slow, it is a lie mostly, in the sense they know it, but don't want to reveal it immediately. Testing the waters on how the conversation is going to to based on this "I don't know".
2. Eye contact When it is said with eye contact and simultaneous nodding of side to side, means the body language, eyes, mind all are telling the truth.
When the eye contact is mostly like starring, head held stationary, means the mind is working on faster, "I don't know" is to buy time, or hide something
3. Response time When it comes even before the question is finished, it is true, they really don't know.
When it is said after a time lapse, even micro seconds, if the above gestures also are in conformance then it is true, if not mostly a calculated lie.