For Slow-Burning Defenses and Village Fortresses, the research time will increase if the keep is under the influence of Mosque. Without any influence, the research times are 3m45s and 5m. With Mosque influence and three scholars, the research time increased to 5m22s and 7m9s.
This bilibili video has shown this effect 【帝国时代4】德里学者:研究?研个P!