Depends on the department, but at least on their social sciences division website they state:
“Only a few programs interview applicants. Those that do will issue invitations via the online application system in January or February. At the time interview invitations are issued, applicants who are not selected to move forward are notified of their decisions. The following programs conduct interviews: Anthropology (PhD) Comparative Human Development (PhD) Political Economy (PhD) Psychology (PhD) Sociology (PhD)."
Hope this helps, but even for the departments listed above, they don't quite seem to interview all admitted students so I guess we never know