A team of researchers has scanned the brains of supporters of a radical Islamist group while asking them about their sacred values and willingness to fight and die for the cause.

Researchers recruited sympathizers of the Al-Qaeda affiliate group Lashkar-et Taiba—the Army of the Righteous. This group carried out the 2008 attacks on Mumbai and is known as a terrorist organization in the U.S., Russia and the European Union. After a long selection process and about two years of gaining their confidence, participants, from Barcelona, Spain, were invited to fMRI facilities.

Anthropologist Scott Atran, one of the study authors, has been investigating the motivation behind the “will to fight” for several years. He noted that in 2016, former President Barack Obama said one of the mistakes made in the war with Iraq was to underestimate militant extremists’ will to fight. Understanding why and to what extent people will fight for causes could be linked to the level of their sacred values.