I'm looking for a word for someone who tends to assume the emotional state of people around them, not necessarily by will. In most definitions that I can find online, being an empath usually implies a psychic ability to attain the emotional state of someone else. I'm looking for a similar word that does not carry connotations of supernatural power, but rather a propensity for taking on the overt emotional atmosphere around them.
The word can be technical, but it doesn't have to be.
Even though I was aware of the tension in the room, I stayed calm. Since Aaron is a(n) ___, he couldn't help but get upset.
I could tell Katy is a(n) ___ because her mood lit up when we joined the celebration.