To study the development of relationships, dr. rajiv carefully observed and recorded patterns of verbal and nonverbal behaviors among boys and girls in the school yard. which research method did dr. rajiv employ?

The research method Dr. Rajiv employed is naturalistic observation.
This is a type of observation that psychologists often use when they want to observe somebody's behavior. In this particular type of observation, the subjects are observed in their natural environment. So, kids playing in the school yard would be a good example.