Dr. Matthews is observing children on the playground and recording instances of aggression. This best illustrates which of the following research methods?

naturalistic observation

Explanation:

When a researcher studies a subject in its natural state it is called naturalistic observation. It is one of the methods of research used by psychologists when they want their study would not be affected by contamination. It has several advantages over other methods as it provide first-hand experience to the researcher, cost-effective and ensured the external validity of research.