Learned Behavior

Some aspects of behavior are influenced by genes, but to what degree can behaviors be modified by experience? Learned behaviors are actions that change with experience. Learning is the modification of a behavior based on experience. Learning can influence the expression of behaviors that are innate and also behaviors that are not innate. The study of learned behavior is central to much of ethology, and learning types can vary from simple to complex.

Habituation

The simplest type of learning, habituation (huh-bi-choo-AY-shuhn), occurs when an animal learns to ignore a frequent, harmless stimulus. For example, when an object passes overhead, a young gull chick tries to hide. As the chick grows older, and as parents, other common birds, or falling leaves pass over the chick's head without consequence, the youngster learns not to react. When a predatory bird flies over, however, the gull stops feeding to hide. Because the passing of a predator's shape is rare, the chicks never habituate to it. Habituation in gulls saves energy and allows feeding, yet preserves defenses for the rare emergency.

Operant Conditioning

A more complex type of learning occurs by trial and error. A dog, for example, learns to associate a cat's hiss and arched back with a painful scratch on the nose. When trial-and-error learning occurs under highly controlled conditions, it is called operant (AH-puhr-uhnt) conditioning. An animal associates some action or operation (the "operant") with a punishment or reward.

American psychologist B. F. Skinner investigated operant conditioning by placing a rat in a box with a lever, such as the one shown in Figure 44-4. As the rat explored the box, the rat eventually pressed the lever, which delivered a food pellet. After several accidental pressings, the rat learned to press the lever deliberately for food. Skinner thought that nearly any behavior could be "conditioned," or trained.

Further research by others, however, showed that although rats can easily learn to press a lever to receive food, they have trouble learning to press a lever to avoid electric shocks to their feet. Rats can learn quite quickly to avoid such foot shocks by jumping. Yet, it's much harder for them to learn to jump to get a food reward. These seeming contradictions do make sense: Rats in nature get food by manipulating objects with their hands, not their feet. Like all animals, rats most easily learn those things that are related to natural skills for survival and reproduction.

Recognizing Learned Behavior

Materials small wads of paper towel (one moist; one dry), T maze made of five pieces of cardboard taped in a T shape inside a cardboard box, sow bug, blunt probe

Procedure

1. Place the moist paper in the left side of the T. Place the dry paper wad on the right side.

2. Place the sow bug at the bottom of the T. If it does not start to crawl, gently prod it with a blunt probe. Observe what the sow bug does when it reaches the T section.

3. Retrieve the sow bug. Perform as many trials as time allows. Record the results of each trial.

Analysis Summarize the sow bug's behavior. Determine if the sow bug modified its behavior through learning. Use evidence to support your answer.

figure 44-4

A rat placed in the "Skinner box" shown here will learn to press a lever to obtain food. This behavior is an example of operant conditioning.

figure 44-4

A rat placed in the "Skinner box" shown here will learn to press a lever to obtain food. This behavior is an example of operant conditioning.

www.scilinks.org Topic: Animal Behavior Keyword: HM60069

Maintained by the

Maintained by the figure 44-5

A chimpanzee will look for a stick and use it as a tool to retrieve termites from the nest for food.

figure 44-5

A chimpanzee will look for a stick and use it as a tool to retrieve termites from the nest for food.

Classical Conditioning

Famed Russian biologist Ivan Pavlov studied another complex type of learning and published his results in 1903. Pavlov observed that dogs salivate at the sight and smell of meat. Was this response learned? To find out, he presented meat to a group of dogs. At the same time that the dogs received the meat, Pavlov would ring a bell. The dogs learned to associate the bell with a meat reward and eventually would salivate in response to the bell tone.

This kind of learning is called classical conditioning. The animal learns to associate a response with a predictive stimulus. The animal responds (salivation) after the natural stimulus (the meat) and learns to associate the natural stimulus with the predictive stimulus (the bell). This type of conditioning differs from operant conditioning in which the animal learns to respond (pushing the lever) before the reward appears (the food pellet).

Classical conditioning occurs in nature as well as in artificial conditions. For example, a crow learns to associate the sight of shiny, broken eggshells on the beach with the presence of newly hatched gull chicks and swoops down for a tasty meal. Advertising agencies capitalize on classical conditioning in humans by associating their product with positive imagery. They associate a certain car brand with financial success, or a certain cola with healthy good looks, all to trigger the desired response: purchase of their product.

Problem-Solving and Reasoning

A more complex type of learning is called problem-solving learning. Figure 44-5 shows an example of problem solving in which a chimpanzee uses a tool to get termites out of a nest. This behavior may be learned from watching a parent, may be a result of trial-and-error, or a combination of several learning mechanisms.

One type of problem-solving, reasoning, involves the ability to solve a problem not previously encountered by the individual in a way that is not dictated by instinct. For example, if a chimpanzee enters a room with boxes scattered on the floor and sees a bunch of bananas tied to the ceiling, the animal will arrange the boxes to form a platform in order to retrieve the bananas.

In another example, researchers placed a jar containing a fish in a tank with an octopus. The octopus used its arms to unscrew the lid, removed the fish, and then discarded the jar and lid. This type of behavior cannot be considered instinctive, because boxes and jars are not in the evolutionary history of these species. The behavior occurred without trial-and-error, as if the animal used reasoning to develop an insight into how to solve the problem.

GENES, LEARNING, AND BEHAVIOR

Biologists have learned from studying bees and other organisms that genes can influence behavior. Some scientists have argued that most behaviors are genetically programmed because different individuals in the same species act in the same ways. Other scientists assert that behaviors are shaped by an animal's experiences. Most ethologists today have come to agree that animal behavior, especially complex behavior such as that seen in primates, is affected both by genes and by experience.

Imprinting

One class of behavior that is determined by both genes and learning is called imprinting. Imprinting is a form of learning in which a young animal forms permanent associations with its environment. The most common imprinting occurs when new-born animals learn to identify a mother figure. Nobel Prize-winning ethologist Konrad Lorenz studied how geese come to identify their mothers and follow them to ponds to feed. Lorenz found that goslings follow the first large object they see moving away from the nest. The goslings would follow wagons, boxes, balloons, and even Lorenz himself, as seen in Figure 44-6.

Another example is found in sea turtles. Sea turtles imprint on characteristics of the beach where they hatch. Years later they are able to find their way back to the same beach to breed.

Imprinting occurs during a specific phase in an animal's development, called a sensitive period. During this time, certain types of learning take place that are later very difficult to change. For example, it is much easier for young children to learn multiple languages. This is much more difficult later in life. Scientists hypothesize that this change in the ability to learn as young animals mature is related to genes that control processes of development.

figure 44-6

These young geese are following Nobel Prize winner Konrad Lorenz. Lorenz cared for the goslings the first day or so after they hatched, and the goslings imprinted on him.

figure 44-6

These young geese are following Nobel Prize winner Konrad Lorenz. Lorenz cared for the goslings the first day or so after they hatched, and the goslings imprinted on him.

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Responses

  • milena girma
    Do sea turtles learn behavior with trial and error?
    3 years ago

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