In this lecture on animal behavior, I have decided to focus exclusively on learning, since this is the one area of animal behavior that tends to appear on the AP Biology exam on a fairly regular basis.
Behavior: Nature or Nurture?
The big question in the back of the mind of most animal behavior researchers today is…
To what extent is animal behavior the result of the following two forces?
Evolutionary forces acting on the genes (nature)
Environmental forces acting during the development of the organism (nurture)
One of the first areas in which these questions were explored was in the area of
instinctive (innate) versus learned behavior.
Instinctive Behavior: “Nature”
The first people to study animal behavior in its natural environment were ethologists—their
field of study is known as ethology.
They were essentially naturalists who observed animals in their natural environments and did experiments in the wild and eventually the lab.
Much of their work supported the genetic basis of behavior.
Three of the most famous researchers won the Nobel Prize in 1973 for their discoveries:
Karl Von Frisch: determined that bees communicate with each other in their hive using the famous “waggle dance” to tell where nectar can be found.
Konrad Lorenz: discovered the phenomenon of imprinting, in which new-born animals learn that the first thing they see and experience must be their mother.
Niko Tinbergen: discovered that animals exhibit fixed action patterns in which a particular sign causes an organism to respond in a stereotypical way.
Complex Innate Behaviors Are Known As Fixed Action Patterns
Innate behaviors are performed without learning or prior experience.
They tend to be very stereotyped, i.e., they are performed the same way each time.
Tinbergen discovered a particular example of this, which he called fixed action
patterns.
An animal experiences a stimulus that is common in its natural environment.
This stimulus will cause a very specific and stereotypic response by the animal.
The stimulus is called a releaser, since it releases a specific stereotypic behavior.
The releaser is generally a very specific characteristic that is necessary for the survival of the organism.
For example, a female red-winged blackbird signals her readiness to mate by raising her tail to a particular angle.
This serves as a releaser for copulatory behavior by the male.
This releaser is so powerful that males will even attempt to copulate with the disembodied tail of a stuffed female, as long as the tail feathers are angled appropriately!
The behavior is called a fixed action pattern because it is the same every time.
Tinbergen noticed that baby herring gull chicks show an instinctive fixed action pattern immediately after hatching.
They would peck on a red spot on their parent's beak, causing the parent to regurgitate food that the chick would then eat.
To determine the particular feature that was the releaser, he selected different, and in some cases exaggerated, features of the stimulus and tested them.
He found that the releasing features of the bill are its:
Long, thin shape
Red color
Presence of color contrasts
He actually got a baby herring gull to peck more frequently at a thin red stick with white stripes than its own mother's bill!
Another example: page 1056 in the book documents Tinbergen's work with the three-spine stickleback fish.
A red fire truck driving by the fish tank elicited a fixed action pattern from this little fish!
The take home message from this research: certain behaviors are truly instinctive, and therefore controlled by the genes.
Unknown sources
Learned Behavior: “Nurture”
Natural selection may favor innate behavior in some circumstances.
It is obviously advantageous for a baby herring gull to know to peck at its parent's beak immediately after hatching.
In other circumstances, such the red-winged blackbird that copulates with a stuffed female, rigidly programmed fixed action patterns may not be useful.
The capacity to make changes in behavior based on experience is called learning.
Simple Learning: Habituation
Habituation is defined as the decline in the response to a repeated stimulus.
The ability to habituate prevents an animal from wasting its energy and attention on irrelevant stimuli.
A brain is not required for this type of learning.
Examples:
The simple protist Stentor retracts when touched, but gradually stops retracting if the touching is continued.
The sea anemone, which also lacks a brain, shows a similar response to touch.
Humans habituate to many stimuli: city dwellers habituate to nighttime traffic sounds, country dwellers habituate to the sounds of crickets and frogs.
Each may initially find the other's habitat unbearably noisy at first, but habituate after a while.
A classic example of habituation in humans is the notion of “crying wolf”:
eventually the person who cries wolf is ignored.
Complex Learning: Conditioning
Conditioning is defined as a learned association between
a stimulus and a response.
An animal learns to perform a response, normally caused by one stimulus, to a new stimulus.
The most famous example of this is Ivan Pavlov's experiments on salivation in dogs:
Pavlov gave the dogs meat (original stimulus), and they salivated (normal
response).
He rang a bell (new stimulus) before the meat (original stimulus)
was given.
This was repeated a number of times.
During this time, the dog was learning to associate the new stimulus
(bell) with the normal response (salivation).
Pavlov rang the bell (new stimulus) without the meat (old stimulus),
and the dog salivated (old response).
2. Operant Conditioning
An animal learns to associate a natural behavior with either reward or punishment.
This kind of conditioning is the method used to train animals—from the family dog to the dolphins at Marine World (generally through rewards rather than punishments).
The most famous example of this is B.F. Skinner's experiments training rats and pigeons in a “Skinner box.”
A rat is placed in a box that has a lever that ejects a food pellet when pressed.
The rat will inevitably bump the lever during its exploration of the box and will be rewarded with a food pellet.
Through repeated exploration of the box the rat will learn to associate a behavior
(pushing the lever) with a reward (food).
The rat has learned what behavior is necessary to perform to obtain food.
Operant conditioning can also be used to train animals to avoid certain behaviors by associating bad behaviors with appropriate punishments.
In nature this same kind of learning is called “trial-and-error learning,”
since it works the same way.
The term “operant conditioning” is generally used for laboratory or controlled situations, but the two are essentially the same
Some researchers and authors claim they are synonymous terms, others draw the distinction I have here.
Examples:
A hungry toad occasionally captures a bee rather than a fly; having its tongue repeatedly stung results in trial-and-error learning so that the toad avoids bees and insects that resemble bees.
Human children learn which foods taste good or bad, that a stove can be hot, and not to pull a cat's tail!
It has been claimed that B.F. Skinner constructed a large Skinner box and raised his second daughter in it.
Furthermore, rumors claim she was so psychologically scared by the experience that she committed suicide in her early twenties.
However, the consensus is that these rumors are false.
Nature vs. Nurture: A False Dichotomy?
As more research is done, it is obvious that most behavior is not exclusively due to nature or to nurture.
An example is imprinting:
In imprinting, learning is governed by innate constraints.
It is a special kind of learning that is rigidly programmed to occur only at certain
critical periods of development.
During this critical or sensitive period of an animal's life (usually right after birth) an animal is primed to learn a specific type of information, which is then incorporated into a behavior that is not easily altered by further experience.
It is best observed in birds such as geese, ducks, and chickens.
Famous example of imprinting: Konrad Lorenz, known as the “father of ethology,” was able to get baby geese to imprint on him and consider him as their mother.
The key idea here is that the baby geese can only learn what is “mom” during a critical period.
The learning is so strong that it is essentially permanent.
The geese imprinted on Konrad would ignore their own species and prefer to follow Konrad.
Later in life they even sometimes initiate courtship behavior with humans!
You can read more about this in the book on page 1061.
