Finding the best dog treat with statistics

This makes me wonder what the research is for whether certain types or breeds of dog prefer certain dog treats, and how individual dogs might develop a preference for one kind over another. Based on this experiment it doesn't seem like the type of meat matters much, since while the top ranked treat is chicken, his second favourite seems to be the duck one.

My dog told me to write that the set of treats is missing non bleached rawhide, other dehydrated meats (eg rabbit, goat, fish), animal parts (eg ears), and vegetables. Also, he volunteers.