I think social sciences research is especially and uniquely interesting for being a lens that peers into the soul of the practitioner like no other type of research can. People who are passionate in researching topics in the social sciences - psychology, politics, sociology, etc - are often that passionate because their research is "me-search"; a substantial part of their work goes towards understanding something about themselves.
Consider the researcher who delves into the psychology of sadness - he has a longing to comprehend how such a profound emotion can have such a grip on his life. The feminist researcher writing sociological papers on female empowerment must somehow feel like her capabilities are undermined by how society regards her biological sex. Then there is the four-time divorced relationship expert, who is so knowledgeable of the dynamics of relationships simply because he is hungry for that ideal relationship he has never been able to attain and can't stop pondering deeply about it. And we may also turn to our friend, the mental health researcher, who is prompted to enter the field because a very close childhood friend of hers suffers from depression.
Many prominent, expert researchers in the social sciences are quite likely good at their specific research interest because within that research interest lies something that will puzzle them for life. That desire to overcome their very own life puzzle can provide the fuel for a life-long obsession with a particular topic or issue.
Essentially, all of such self-directed research, or me-search, stems from a deep-seated need to understand issues that plague the restless researcher so that, from understanding, he can control the problem and ultimately justify either his desires and actions, or his inability to overcome the forces that hold him back.
So, budding social scientists, what personal demon of yours is going to both torment and consume you, and at the same time make you produce great bodies of literature?