23.1 Stereotyped and Learned Behavior
Key Takeaways
A fixed action pattern is a stereotyped sequence triggered by a sign stimulus and run to completion, as when a graylag goose retrieves an egg or a male stickleback attacks a red underside.
Taxis is directed movement toward or away from a stimulus, while kinesis is a change in speed or turning, not a compass direction.
Habituation is ignoring a repeated harmless stimulus, and imprinting is learning limited to a sensitive period, as in Lorenz's goslings.
Classical conditioning pairs a neutral stimulus with one that already causes a response; operant conditioning changes a behavior because of its consequence.
A courtship display can be an innate social signal, and a fixed action pattern is not operant conditioning.
23.1 Stereotyped and Learned Behavior
A CLEP behavior item describes a short scene and asks you to name the mechanism. Stereotyped behavior is species-typical. It appears in a usable form without practice, and one performance looks much like the next. Learned behavior changes because of experience.
Fixed action patterns
A fixed action pattern is a stereotyped sequence triggered by a sign stimulus and run to completion. The sign stimulus, also called a releaser, is the simple cue that starts the sequence. Once the sequence begins, the animal typically finishes the motor pattern even if that cue is taken away. A reward does not have to follow each step.
The graylag goose retrieving an egg is the classic case. A nesting goose sees an egg outside the nest cup. She reaches with her bill, tucks the egg against the underside of her neck, and rolls it home with a side-to-side correction. If the egg is removed after she has started, she often continues the retrieval motion through empty space until the sequence ends. She will also roll other egg-shaped objects.
The male three-spined stickleback shows the same release in a fight. In breeding condition his underside is red, and he attacks other red-bellied males near the nest. Niko Tinbergen found that a crude model with a red underside releases the attack, while a detailed fish model that lacks red often does not. The red underside is the sign stimulus. The charge is the fixed action pattern.
Taxis and kinesis
Taxis is directed movement toward or away from a stimulus. Movement toward the source is positive taxis, and movement away is negative taxis. Phototaxis uses light, and chemotaxis uses a chemical. A swimming Euglena moving toward light is positive phototaxis. A male moth moving toward the source of a female's scent is chemotaxis.
Kinesis is a change in speed or turning, not a compass direction. In orthokinesis, speed depends on stimulus intensity. In klinokinesis, the rate of turning changes. Woodlice are the classroom case. In dry air they move faster and turn more often. In a damp crevice they slow down and turn less, so they tend to remain where humidity is favorable. No step is aimed at the moisture.
Learned behavior
Habituation is learning to ignore a repeated harmless stimulus. The response declines even though the animal can still sense the cue and can still move. A hydra stops contracting after many gentle touches. A young bird stops crouching when the same harmless shadow passes again and again. A new stimulus can restore a response, which separates habituation from simple exhaustion.
Imprinting is learning limited to a sensitive period, also called a critical period. Konrad Lorenz showed that greylag goslings follow the first conspicuous moving object they see in the hours after hatching and later direct social behavior toward that object. The object can be Lorenz himself. Exposure long after hatching does not produce the same following. That early window is filial imprinting, not ordinary practice at any later age.
Conditioning and problem solving
Classical conditioning pairs a neutral stimulus with a stimulus that already causes a response. In Ivan Pavlov's work, food in a dog's mouth already caused salivation, and a bell did not. After the bell reliably came before the food, the bell alone elicited salivation. Food is the unconditioned stimulus, salivation to food is the unconditioned response, the bell becomes the conditioned stimulus, and salivation to the bell is the conditioned response.
Operant conditioning changes a behavior because of a consequence. In B. F. Skinner's experiments, a rat pressed a lever and food followed, so lever pressing became more common. A consequence that makes a behavior more common is reinforcement. A consequence that makes it less common is punishment. Trial-and-error learning, as when Edward Thorndike's cats worked at a puzzle-box latch, and insight, as when Wolfgang Kohler's chimpanzees suddenly stacked boxes to reach fruit, are problem-solving forms of learning, not the pairing of a neutral cue with a reflex.
Innate social signals
Social signals can be innate. A courtship display is often a species-typical sequence that a mature animal performs without being taught the steps. The male stickleback's zigzag approach to a female is a courtship fixed action pattern, just as his attack on red is an aggressive one. The form of the display was not copied from a tutor. Learned social signals also occur: many songbirds memorize an adult song during a sensitive period.
| Comparison | Innate example | Learned example |
|---|---|---|
| Motor pattern | A fixed action pattern runs to completion after a sign stimulus, as in graylag goose egg retrieval or a stickleback attack on a red underside | Operant conditioning: a rat presses a lever more often because food follows the press |
| Orientation or cue | Taxis is directed, as when Euglena swims toward light; kinesis changes speed or turning with no compass direction, as in a woodlouse in dry air | Classical conditioning: a neutral bell paired with food comes to elicit salivation |
| Social behavior | A courtship display can be innate, as in the stickleback zigzag approach | Imprinting is limited to a sensitive period, as when Lorenz's goslings follow; habituation is ignoring a repeated harmless stimulus |
Warning
A fixed action pattern is not operant conditioning. The goose finishes the egg roll without a trainer's reward, and the stickleback attacks a red underside without a payment after the charge. Imprinting is limited to a sensitive period rather than being ordinary practice at any age.
Sorting a behavior scene
Match the name to the evidence in the scene: a sign stimulus and a finished sequence, a heading toward or away from a source, a change in speed or turning, a fading response to a harmless repeat, an early sensitive period, a neutral cue paired with an old reflex, or a consequence that changes how often an act is performed.
A male three-spined stickleback in breeding condition attacks a crude model with a red underside and ignores a realistic fish model that lacks red. Each attack follows a similar sequence. What is this behavior?
Imprinting that can be established equally well by practice at any age.
Habituation, because repeated exposure has trained the fish to ignore a harmless shape.
Operant conditioning, because a trainer rewarded each charge.
A fixed action pattern released by a sign stimulus.
Woodlice walk quickly and turn often on a dry surface. In a damp crevice they slow down and turn less. Observers record no consistent heading toward the moisture. Which term fits?
Positive taxis, because each turn is a heading toward the moisture.
Kinesis, because speed and turning change without a compass direction.
Insight learning, because the animal suddenly reorganizes a path toward a goal.
Classical conditioning, because dry air is a neutral cue paired with an existing reflex.
Greylag goslings that first saw Konrad Lorenz in the hours after hatching followed him and later directed social behavior toward him. Goslings whose first exposure came long after hatching did not form the same following. Which statement is correct?
This is kinesis, because the birds changed speed without a direction.
This is habituation, because the goslings learned to ignore a repeated harmless stimulus.
This is imprinting, and it is limited to a sensitive period.
This is operant conditioning that can be established by ordinary practice at any age.
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