Placid

adj. not easily upset or excited

Sitting in the audience, I discovered that man beside me had a very placid nature because he did not laugh at any of the comedian's jokes.

Empathy

n. the ability to understand and share the feelings of another

When my friend's mother was diagnosed with breast cancer, I was able to feel empathy because my grandmother had previously had breast cancer.

Pathological

adj. 1. of or relating to pathology
       2. involving, caused by, or of the nature of physical or mental disease
       3. compulsive; obsessive

In Mean Girls, a teen movie, one of the supporting characters is a pathological lier and cannot help lying to everyone around her.