"The human infant enters the world without information about what is edible and what is not," wrote psychologist Paul Rozin, who studied disgust for many years at the University of Pennsylvania. Until kids are around two, you can get them to try pretty much anything, and Rozin did. In one memorable study, he tallied the percentage of children aged sixteen to twenty-nine months who ate or tasted the following items presented to them on a plate: fish eggs (60 percent), dish soap (79 percent), cookies topped with ketchup (94 percent), a dead (sterilized) grasshopper (30 percent), and artfully coiled peanut butter scented with Limburger cheese and presented as "dog-doo" (55 percent). The lowest-ranked item, at 15 percent acceptance, was a human hair.
pp.66-67 of Mary Roach, Gulp.