Fifteen-month-old Regina is at the build-a-bear workshop in the city with her mother nearby, when an unfamiliar man says to her, "What a nice bear you are building!" Regina promptly looks to her mother, as if for guidance. Her mother smiles at the presence of the man, and Regina continues building her bear. Regina's checking with her mother is a type of:

Social Referencing.

Explanation:

Social Referencing is a process in which an infant learns to take cues from the behaviors, emotions, and actions of the adults around them, especially parents or caretakers. In this process, they take cues by looking at the facial expressions of parents or caretakers to know how to respond in a certain situation.

In the given case, Regina's looking at her mother when an unfamiliar man approached her exemplifies social referencing. She was referring to the facial expressions of her mother on how to react at this approach of a strange person.

Thus the correct answer is social referencing.