Final answer:
The psychologist's act of joining a local commune to observe its social interactions is an ethnographic study, which is a qualitative research approach involving a researcher's long-term, immersive participation in a community to understand its members' social practices and cultural meanings.
Step-by-step explanation:
The psychologist joining a local commune to observe and understand its members social interactions would be engaging in a type of ethnography. This research approach is a qualitative method where researchers immerse themselves in a community to gather data by experiencing and observing social interactions and practices within that group. The goal of ethnography is to gain a deeper understanding of the community's ways of life, which often involves the researcher becoming a participant in the environment they are studying.
Unlike simple participant observation or other research methods, ethnography is characterized by long-term, in-depth engagement with the subject community. It's aimed not just at observing behaviors, but also at understanding the meaning and significance of those behaviors from the perspective of the community members. Ethnographers might live with their subjects, engage in the same activities, and try to experience life as their subjects do. This method provides a rich, detailed, and comprehensive view of the studied cultural or social group.
In the context of this question, by joining a local commune, the psychologist would be conducting an ethnographic study to collect information through participatory observation, thus choosing to immerse themselves directly into the culture. Answering multiple-choice questions that might accompany this information, ethnography is not based on hypothesis testing (choice a), it can involve subjects potentially being unaware of the study if revealing the researcher's identity would alter the subject's behavior (choice b), it doesn't exclusively involve minority ethnic groups (choice c), and it focuses on understanding how the community sees themselves in relation to their social milieu (choice d).