From my experience, it appears that only those who have looked into both the social and the psychological, achieve any kind of meaningful understanding of how society and humans work. When the scientist's blind spot includes an entire dimension of the human condition, all their work will amount to an exercise in futility. In (the more familiar to me) case of anthropologists, often deliberately ignoring the psychological aspects of observed practices (e.g., in Rabinow's Reflections on Fieldwork in Morocco) results in culturalist reductionism, where perhaps the most important aspect of a ritual is omitted.
This understanding, however, is hard to win allies for. I remember Scott Lash, who himself studied both sociology and psychology, warning me that I would hardly come across academics even aware of the issue, let alone interested in any aspects or implications of it. Looking on both sides of the dark veil separating social and psychological facts, creates a transformational experience, a true Zen moment, a temporary dissolution of the object/subject separation, whose memory, however, lasts and influences all your perceptions for the rest of your lifetime. That is why, I would never be truthful, should I have to stick to only one part of the proverbial elephant. The blindfold may have been off for just a moment, but after that there's no way back.