1. Lesson Overview
29.1 Elements of Behavior

2. Behavior and Evolution
Behavior is the way an organism reacts to stimuli in
its environment.
A behavior can be simple – a dog turning its head in
response to a noise. Others can be complex – an animal
washing its food before eating it.
Usually, behaviors are performed when an animal detects and responds to some sort of stimulus in its environment. The way an animal responds to a stimulus, however, often depends on its internal condition.
Many behaviors are essential to survival. To survive and reproduce, animals must be able to find and catch food, select habitats, avoid predators, and find mates. Behaviors that make these activities possible are just as important to survival as physical characteristics like teeth and claws.

3. Behavior and Evolution
Remember, physical traits are shaped by instructions coded in the genome.
The nervous system, which makes behavior possible, is influenced by genes.
Therefore, it should come as no surprise that some behaviors are influenced by genes and can therefore be inherited.
If a behavior that is influenced by genes
increases an individual’s fitness, that
behavior will tend to spread through a
population. Over many generations, various
kinds of adaptive behaviors can play central
roles in the survival of populations and species.

4. Behavior and Evolution
The genes that code for the behavior of the moth helps it escape predators.
If disturbed, the moth will move its front wings to expose a striking circular pattern on its hind wings. This behavior may scare off predators that mistake the moth’s hind-wing pattern for the eyes of a predator.

5. Innate Behavior
Why do newly hatched birds beg for food within moments after hatching?
How does a spider know how to spin its web?
These are innate behaviors.
Innate behaviors appear in fully functional form the first time they are performed, even though the animal has had no previous experience with the stimuli to which it responds.

6. Innate Behavior Innate behaviors are also called instincts.
The suckling of a newborn mammal is a
classic example of a simple innate behavior.
Other innate behaviors, such as building
nests by weaver birds, can be complex.
All innate behaviors depend on patterns of nervous system activity that develop through complex interactions between genes and the environment.
Innate behaviors enable animals to perform certain tasks essential to survival without the need for experience.

7. Learned Behavior
If all behaviors were innate, animals would have a tough time adapting to unpredictable changes in their environments. Many complex animals live in unpredictable environments, where their fitness depends on behaviors that can be altered as a result of experience.
Acquiring changes in behavior during an animal’s lifetime is called learning.
Many animals have the ability to learn.
Organisms with simple nervous systems, like sea stars, shrimp, and most other invertebrates, learn only rarely.

8. Learned Behavior
A few invertebrates, and many chordates, learning is common and occurs under a wide range of circumstances.
This chimpanzee is exhibiting a complex learned behavior—using a tool to “fish” for termites.
Scientists have identified several different ways of learning - habituation, classical conditioning, operant conditioning, and insight learning.

9. Habituation
Habituation, the simplest type of learning, is a process by which an animal decreases or stops its response to a repetitive stimulus that neither rewards nor harms the animal.
Often, learning to ignore a stimulus that offers neither a reward nor a threat can enable an individual to spend its time and energy more efficiently.

10. Habituation
Birds on the side of a road take flight when a car approaches (left). After the passage of many cars, which haven’t harmed them, the birds no longer take flight when one approaches (right). The birds have become habituated to the stimulus of passing cars.

11. Classical Conditioning
Classical conditioning is a type of learning in which a certain stimulus comes to produce a particular response, usually through association with a positive or negative experience.
For example, you go to a restaurant and eat food that you have never tried before. Shortly after beginning to eat, you get sick
from a stomach virus. From that time on, you
feel sick whenever you smell that food. In this
case, a negative experience, the stimulus is the
smell of that particular food, and the response is
nausea.
The food didn’t make you sick, but you have
been conditioned to associate the smell of that
food with illness.

12. Classical Conditioning
Classical conditioning was first described around 1900 by Russian physiologist Ivan Pavlov, who was studying dogs’ responses to food.

13. Operant Conditioning Conditioning is often used to train animals.
Operant conditioning occurs when an animal learns to behave in a certain way, through repeated practice, to receive a reward or avoid punishment.
This type of conditioning was first described in the 1940’s by an American psychologist B. F. Skinner. He invented a testing procedure that used a box called a “Skinner box.” A “Skinner box” contains a colored button or lever that delivers a food reward when pressed. After an animal is rewarded several times, it learns that it gets food whenever it presses a button or lever.

14. Operant Conditioning
A dog randomly brushes its tail against a bell hanging on a doorknob.
The owner responds by opening the door to let the dog outside.
After the “ring the bell; open the door” sequence has occurred several times, the dog has learned to ring the bell when it wants to go out. The dog has learned by operant conditioning how to be let out of the house.

15. Operant Conditioning
Operant conditioning is sometimes described as a form of trial-and-error learning. Trial-and-error learning begins with a random behavior that is rewarded in an event called a trial. Most trials result in errors, but occasionally a trial will lead to a reward or punishment.

16. Insight Learning
The most complicated form of learning is insight learning, or reasoning.
Insight learning occurs when an animal applies something it has already learned to a new situation, without a period of trial and error.
Insight learning is common among humans and some other primates.
In one experiment, a hungry chimpanzee used insight learning to figure out how to reach a bunch of bananas hanging overhead: It stacked some boxes on top of one another and climbed to the top of the stack.

17. Complex Behaviors
Though behaviors may be learned, they often involve significant innate components.
Therefore, many complex behaviors combine innate behavior with learning.
Young white-crowned sparrows have
an innate ability to recognize their
own species’ song and to distinguish
it from the songs of other species.
To sing their complete species-specific
song, however, young birds must hear
it sung by adults.

18. Complex Behaviors
Some animals recognize and follow the first moving object that they see in their early lives. This process is called imprinting and it involves both innate and learned behavior.
Young birds have an innate urge to follow
the first moving object they see. But they
are not born knowing what that object
will look like, so they must learn from
experience what to follow.
These baby sandhill cranes have
imprinted on their mother and will
follow her in flight.

19. Complex Behaviors
Once imprinting has occurred, the behavior becomes fixed. Sometimes, the fixed object of imprinting shows up later in life.
When baby geese mature, they search for mates who resemble the individual on whom they imprinted on as goslings. In nature, this is almost always their mother, and therefore a member of their own species.

20. Complex Behaviors Sometimes, animals imprint on objects.
For example, in an experiment, recently
hatched cranes raised in captivity imprinted
on a hand puppet. Later, that puppet is used
to help introduce these birds to the wild by
guiding them along a migration route that
they would normally learn by following their
parents.

21. Complex Behaviors
Animals can imprint on sounds, odors, or any other sensory cues.
Newly hatched salmon imprint on the odor of the stream in which they hatch. Young salmon then head out to sea. Years later, when they mature, the salmon remember the odor of their home stream and return there to spawn.