Immediate Assumption

I had a conversation with brief conversation with and co-worker this morning. She asked me something and I answered. Her immediately replied that I was lying. I answered here truthfully and never recalled lying to her before. How could that be that she assumed that i was lying? This did not just happen today, I had many conversations like this before.

Reactions like this puzzles me. Why do some people assume that we are lying when we answer them? Are we used with lies that we cannot decide which is the true or false? Are we not trustful of everyone around us? What makes a person assume that answers are lies?

This reminds me of a friend who always react by saying that I was lying to everything I tell her. I always ask her if i have ever lied to her and she cannot answer me straight because I have never lied to her before. I am always irritated with this type of response because I am not someone who fabricates answers. What makes them think that I'm lying? Is it because I sometimes smile when I answer or that I answer immediately to their questions. I really have no clue why this is their initial reaction to my answers. Maybe the truth fo them is harder to believe than a lie. Who knows?