Dogs have food prejudices

T
his article about where dogs originated contains this quote
about research methodology:

Dr. Boyko traveled to a number of the locations where blood was drawn from village dogs. He said: “The great thing about working with dogs is that if you show up with food you don’t usually have trouble recruiting subjects. Usually.”

He added: “We showed up in Puerto Rico at a fishing village and the dogs turned up their noses at roast beef sandwiches. They were used to eating fish entrails.”