Nikolaas Tinbergen was a Dutch zoologist who won a Nobel prize for physiology/medicine in 1973. His work included the study of supernormal stimuli. This concept states that an instinctive response of an animal to a natural stimulus can be amplified through the use of artificial means. One experiment was with stickleback fish. The male stickleback fish will attack a false wooden fish model of another male more viciously that a real male if the belly of the model as painted more red than a real fish. In doing this, the natural attacking stimulus of the red belly (the sign stimulus) was exaggerated by making the color more noticeable. The natural drive for the fish to attack is an example of a fixed action pattern, or an instinctive reflex that an animal cannot help but perform in response to the sign stimulus.