Final answer:
The term that describes a lack of emotions and an expressionless face is 'flat affect,' which is a reduction in emotional expressiveness seen in various mental health conditions.
Step-by-step explanation:
The term used to describe a lack of emotions and an expressionless face is flat affect. This psychological term is often associated with various mental health conditions, including schizophrenia, depression, and autism spectrum disorders. A flat affect implies a severe reduction in emotional expressiveness where a person's voice may become monotonous, and they show little to no facial expressions.
People with flat affect may not react to situations in a way that would be expected for the context or the emotional content of the conversation or event. It's important to note that while they may appear emotionless, they may still be experiencing emotions internally. This condition can be contrasted with other affective disorders like apathy (lack of interest or enthusiasm), anhedonia (inability to feel pleasure), and alexithymia (difficulty in identifying and expressing emotions).