His ethnography of the Trobriand Islands described the complex institution of the Kula ring and became foundational for subsequent theories of reciprocity and exchange. He was also widely regarded as an eminent fieldworker and his texts regarding the anthropological field methods were foundational to early anthropology, for example coining the term participatory observation. His approach to social theory was a brand of psychological functionalism emphasising how social and cultural institutions serve basic human needs, a perspective opposed to A. R. Radcliffe-Brown's structural functionalism that emphasised the ways in which social institutions function in relation to society as a whole.