Most psychopaths have a very shallow affect. That is, our emotions tend to be shallow in general. They are also short-lived. Now, that said, the presence of other personality disorders, most notably Borderline Personality Disorder, can cause this criterion of psychopathy to become somewhat muddy. It can also be difficult to tease the shallow affect of psychopathy from our inability to feel affective empathy or guilt and remorse.
When my mother was in critical condition a few days ago, I did not feel sadness, despair, or any other emotions that most neurotypicals would have when presented with the real possibility of losing a loved one. I was completely stoic except for the adrenaline rush caused by the intellectual realization that a high-stakes game was unfolding before me. My therapist is often stunned by the lack of emotion that I present in session. We talk of my many accomplishments, both saintly and sinful, and there is nothing but stoicism as the words recounting such pour from my mouth. In my writing, I try to avoid any portrayal of emotion as it would be false. There is simply nothing – usually – there.