Answer:
This textbook's discussion is related to the Lecture #1 from the Karla Emeno Psychology textbook series "Welcome" course Introductory Psychology.
This phenomenon is best explained by "The Chameleon Effect", associated with nonconscious mimicry behavior in people's social environments, when people mimic the behavior of others in certain social settings.
Mirroring is akin to this concept, the subconcious replication takes place to set up a sense of empathy that helps to understand the other person's emotions.