Final answer:
The terms 'Flat - no expression' and 'Over - expressive' describe affect, which is the visible expression of emotions as observed through body language or facial expressions.
Step-by-step explanation:
The description of being 'Flat - no expression' and 'Over - expressive' pertains to the psychological concept of affect. Affect refers to the visible expression of emotion, often observed through body language or facial expressions. When someone shows a flat affect, it implies a lack of visible emotion or expression, which could be characteristic of certain psychological conditions. On the other hand, being over-expressive may indicate an exaggerated display of emotions. This is related to and often confused with mood, which is a more prolonged emotional state that may not be immediately observable. Emotions can be momentarily intense and typically reflect a response to a specific event or situation. Conversely, mood represents a more persistent state of feeling that can color one's perception over time.