Muslims who undertake the hajj "return with more positive views towards people from other countries," are more likely to say "that people of different religions are equal," and are twice as likely as other religious Muslims to condemn Osama bin Laden, the study found.

Hajjis are also more likely to back education for girls and work for women, the study found.

Going on the hajj, which all Muslims must do at least once if they are able, can also embolden women to challenge religious authority when they return home.

Khwaja chuckled at the Mark Twain quote: "Travel is fatal to prejudice, bigotry, and narrow-mindedness." But Khwaja said it was not simply travel that changed pilgrims -- it was seeing unfamiliar practices in the holiest of settings.

And indeed, Khwaja said, going on the hajj makes pilgrims less likely to observe strictly local customs, such as the use of amulets.