Do monkeys mind poop in their food?
In the 1950s, scientists discovered that rhesus macaques in Japan washed their food before they ate it. Recently, other studies have tried to determine if the monkeys really care if their food is dirty. Experimental methods included rolling sweet potato chunks in sand, and placing wheat grains or peanuts on real monkey poo, or fake poo. I won't give away the ending, you should read about it yourself!