Do you not feel emotions, or do you not feel empathy?
The former is called alexithymia. It literally means "no words for emotions", and is experienced as an inability to identify emotional states in oneself. A person may still experience emotions and act on them, but they're unaware of which emotion they're feeling at any given time - for example, they may snap at or say something nasty to a close acquaintance, but be unaware that they were angry or that their words would be hurtful to the other person. Alexithymia isn't a disorder in itself, but it's a symptom that can indicate other disorders. Common causes include dismissive/avoidant attachment disorder, autism spectrum disorders, avoidant or schizoid personality disorders, or sometimes PTSD and emotional trauma.
Lack of empathy means an inability to put yourself in someone else's shoes and imagine someone else's perspective. It's actually divided into two categories: a deficiency in emotional empathy means an inability to understand others' emotional states (and is closely related to alexithymia, as you usually can't identify emotions in others if you can't identify them in yourself) and is commonly associated with sociopathy, schizophrenia, and narcissism; while cognitive empathy is your ability to imagine yourself in another's shoes and take on their perspective given their differing information, and is frequently deficient with autism spectrum disorders, bipolar disorder, or borderline personality disorder.
Sociopaths or psychopaths, (the two can be used interchangeable according to Hare) can identify emotions, but they don't register as something to feel as well or to mirror. That is where the "game" comes from. You can use peoples emotions and the little clues they drop in body language against them to efficiently and effectively manipulate them into doing what you want them to do.
The former is called alexithymia. It literally means "no words for emotions", and is experienced as an inability to identify emotional states in oneself. A person may still experience emotions and act on them, but they're unaware of which emotion they're feeling at any given time - for example, they may snap at or say something nasty to a close acquaintance, but be unaware that they were angry or that their words would be hurtful to the other person. Alexithymia isn't a disorder in itself, but it's a symptom that can indicate other disorders. Common causes include dismissive/avoidant attachment disorder, autism spectrum disorders, avoidant or schizoid personality disorders, or sometimes PTSD and emotional trauma.
Lack of empathy means an inability to put yourself in someone else's shoes and imagine someone else's perspective. It's actually divided into two categories: a deficiency in emotional empathy means an inability to understand others' emotional states (and is closely related to alexithymia, as you usually can't identify emotions in others if you can't identify them in yourself) and is commonly associated with sociopathy, schizophrenia, and narcissism; while cognitive empathy is your ability to imagine yourself in another's shoes and take on their perspective given their differing information, and is frequently deficient with autism spectrum disorders, bipolar disorder, or borderline personality disorder.