A technique used to determine an animal's response to a stimulus and its sensory powers. Geese, gulls, and other birds roll into their nests any egg they find outside the nest. Herring gulls (Larus argentatus) react more strongly to large eggs than to small ones regardless of their shape and prefer stippled eggs to those without stippling. Karl von Frisch used food rewards to train minnows to distinguish colours and catfish to respond to a whistle, demonstrating that minnows are not colour-blind and catfish are not deaf.
Subjects: Zoology and Animal Sciences.