Related to the medical term "blunted affect"
Dysthymia: a mood disorder that has a number of typical characteristics: low energy and drive, low self-esteem, and a low capacity for pleasure in everyday life [...] They will usually find little pleasure in usual activities and pastimes
is a personality construct characterized by the sub-clinical inability to identify and describe emotions in the self. The core characteristics of alexithymia are marked dysfunction in emotional awareness, social attachment, and interpersonal relating. Furthermore, individuals suffering from alexithymia also have difficulty in distinguishing and appreciating the emotions of others, which is thought to lead to unempathic and ineffective emotional responding
Adjectives to describe someone who is emotionally shallow and lacking in empathy
Insensitive lacking feeling or tact = so insensitive as to laugh at someone in pain
Non empathic to be incapable of recognizing emotions that are being experienced by another person.
Emotionless showing, having, or expressing no emotion
Callous 2. a feeling no emotion b : feeling or showing no sympathy for others