"Laughter is not the first sound that comes to mind when someone mentions Arabia. As Khuri wrote, "In Arab culture, laughing loudly in public demeans one's character." Prostitutes laugh, and inferior males, but powerful men are solemn. As Khuri noted, an Arab avoids displaying a light heart. Typically, an American being photographed puts on a smile; an Arab adopts a look so solemn it would be appropriate for Judgment Day." (thanks Waleed)
PS The late Fouad Khuri was a lousy Lebanese anthropologist who assumed that mimicking Raphael Patai would propel him into Western acclaim. He also romanticized Shi`ites in a very patronizing way--even in person.