Sometimes emotions or physical condition cloud communication. What a listener calls irritability can really be fatigue. What is read as apathy can mean a headache. Shyness is regularly labeled aloofness. Defensiveness grows out of fear but is often expressed as aggression or anger.
Uncertainty leads to cautious, quiet behavior.
Lack of concentration can actually be an expression of nervousness about another issue entirely. And my vacant stare can just mean I took too much allergy medicine. Sometimes emotional responses to our remarks are so obviously out of place we can easily suspect our interpretations are wrong. As a professor, I am periodically baffled by students' explosive anger and almost frantic responses. Student behavior I respond to as anger is really anxiety.