Need I say more?
No specularity, Ambient Oclusion.
https://blenderartists.org/forum/viewtopic.php?t=57016&highlight=clay
https://blenderartists.org/forum/viewtopic.php?t=49278&highlight=clay
https://blenderartists.org/forum/viewtopic.php?t=30131&highlight=clay
need i say more? please search next time.