Final answer:
A psychologist studying high school students' social interactions at a mall is practicing observational research, focusing on naturally occurring social patterns without manipulation of variables.
Step-by-step explanation:
A psychologist observing high school student interactions at a mall to learn about the formation of social groups is conducting observational research. This type of research involves recording and analyzing naturally occurring phenomena without manipulating the independent variable. It allows researchers to gather data on social patterns and roles in certain contexts, providing descriptive or interpretive results rather than quantitative data. Studies such as participant observation, where researchers immerse themselves in a group to observe it from within, are common methods employed to obtain a deep understanding of the subject matter.