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Summary: Classic Ethology

Ethology, the European science of animal behavior, developed out of zoology and emphasized instinctive behaviors. Tinbergen and Lorenz were two giants in the field of ethology.

Tinbergen published an influential book in 1951 and followed it up with a 1952 article in Scientific American introducing ethology to many Americans. Tinbergen described how a little fish went through a complex series of behaviors during mating season, each triggered by a specific stimulus.

Species-typical behaviors are often listed in an ethogram compiled by close observation. A species-typical behavior can also be called an instinctive behavior, innate behavior, fixed action pattern, action pattern, motor program or wired-in behavior.

In 1938, Tinbergen and Lorenz collaborated on an article describing the egg-retrieving behavior of the greylag goose. The egg-retrieval movement shows many characteristics typical of motor programs.

The behavior is stereotyped or fixed in form. It is set off by a highly specific stimulus called a sign stimulus or releaser. Once triggered, the action runs to completion (endogenous running-out).

Lorenz showed that the egg-retrieval response was also triggered by a supernormal stimulus: a gigantic egg. Supernormal stimuli are exaggerated sign stimuli that trigger a stronger than normal response from an animal.

Lorenz brought attention to imprinting: the process in which baby ground-dwelling birds learn to follow the first object they see after hatching. Lorenz let baby greylag geese imprint upon him, and they followed him all around his farm.

Babyishness is another pattern pointed out by Lorenz. He observed that all baby animals have a distinctive look.

The features of babyishness include prominent foreheads, large eyes, soft jaws, fuzzy or furry bodies, and stubby limbs. These stimuli trigger merciful, parenting behavior in a variety of species, birds as well as mammals, sometimes resulting in cross-species adoption.

Originally, researchers assumed that all associations were equally easy to learn. Ethologists drew attention to the impor­tance of evolutionary influences on learning.

Some forms of learning are more natural and easier because animals are prepared for them by evolved neural mechanisms. Examples are the digger wasp's ability to memorize the area around its nest and human tendencies to fear spiders and snakes.

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