When there is a loud sound, you quickly jump without thinking. This is because this reflex is an innate, or inherited, behavior. In this lesson, we will look at reflexes as well as several other types of innate behaviors.
Innate Behavior Overview
Behavior can be described as a reaction to a stimulus, which is an internal or external event that leads to a response. Many forms of behavior are essential to an organism's survival.
Examples of behaviors range from hunting skills to avoiding predators to migrating south in the winter to mating rituals.
In this lesson, we will focus on innate behaviors, which are often called inherited or instinctive behaviors. These can be very simple or complex. Innate behaviors are fully functional the first time they are performed - even without previous exposure to the stimulus.
Let's look at the types of innate behaviors, as well as some examples, as we follow Craig through his day.
Reflexes, Taxes and Kineses
First, we will look at the most simple forms of innate behavior: reflex, taxis and kinesis.
Today, Craig has a doctor's appointment. As part of his physical, the doctor says that she is going to test Craig's reflexes. A reflex is an automatic response to a stimulus. In order to test his reflexes, the doctor uses a small rubber hammer to hit Craig's knee. When she does this, Craig's leg immediately kicks up. Even though Craig hasn't had this done before, because reflexes are innate, this reaction occurs without previous exposure to the stimulus.
After leaving the doctor's office, Craig decides to go for a walk near a pond. Unfortunately, he quickly discovers that there are several mosquitoes flying around. Mosquitoes react to the carbon dioxide that Craig's body releases. This movement of the mosquitoes is known as taxis. A taxis is a response to a stimulus resulting in movement towards or away from the stimulus. Other examples of taxis include gravitaxis, which is movement towards or away from the pull of gravity, and thermotaxis, which is the movement toward or away from heat.
Craig decides that he does not enjoy being the victim of mosquito bites and instead heads home. As soon as he turns on the light in the hallway, he sees something small run across the floor. The reaction of this cockroach is an example of kinesis. Kinesis is the movement of an organism in response to a stimulus, but it does not result in movement directly towards or away from the stimulus. This can be a little challenging to differentiate from taxis, so let's compare the reaction of the mosquito to carbon dioxide and the cockroach to light. Remember that with taxis, the mosquito moves towards the carbon dioxide source in order to find food. However, when a light is turned on, the cockroach will quickly start running - not necessarily away from or towards the light. This is kinesis, as it is just movement as a response to the stimulus of the light being turned on and not associated with a direction.
Fixed Action Patterns and Migration
Now that we have the basics down, let's move on to more complex forms of innate behavior: fixed action patterns, migration, stereotypy and circadian rhythms.
After seeing the cockroach run across his floor, Craig decides that being at home may not be the best idea. Instead, he goes for a walk in the park (not near a lake this time). He notices a few birds in the trees singing and making some funny head movements. Because it is spring, he realizes that these birds may be going through mating rituals and remembers that many birds have complex sequences of actions and songs - even some funny dance moves - when it comes to mating. This is an example of a fixed action pattern, or a set sequence of movements triggered by a stimulus. These are more complex than those just seen with a reflex, taxis or kinesis. When the stimulus of the presence of a female bird occurs, a male will go through a specific sequence of movements in order to attract his potential mate.
While Craig does enjoy the songs of the birds, as he tries to watch his step on the path to avoid stepping in anything unpleasant under the tree, he cannot wait until the birds fly south again in the winter. This behavior is called migration, and is the seasonal movement from one area to another. Craig remembers that migration can also be seen in other species, including whales, which migrate in order to find water best suited for breeding and for feeding. Warmer water is good for breeding and giving birth, but colder water is generally better for feeding.
Stereotypy and Circadian Rhythms
Thinking about whales makes Craig want to go to the aquarium. He enjoys watching the animals swim around in the huge tanks, but sometimes wonders if the animals are happy. Craig remembers seeing some animals in small cages at the zoo repeatedly pacing back and forth or even hurting themselves. One time he saw a bird that had almost no feathers left. When he asked if the bird was ill, he was told that it just keeps pruning and won't stop this behavior. These actions are known as stereotypy or stereotyped behavior. This is a repetitive or ritualistic movement, posture or utterance. Examples in humans and primates include pacing, rocking or tilting one's head. In humans, stereotypy is often associated with people who are diagnosed with autism as there are sometimes repeated behaviors seen in these people (most commonly when they are in stressful situations). With the animals Craig saw at the zoo, it was most likely stress and sensory deprivation that caused the stereotypy.
After his long day of visiting the doctor, avoiding the mosquitoes, seeing the cockroach, hearing the birds try to find a mate and wishing they would fly south and finally visiting the aquarium, Craig feels very tired. Also, it is starting to get dark outside and Craig normally feels sleepy when the sun starts to go down. This feeling of needing to get some sleep is related to Craig's internal biological clock but is best known as a circadian rhythm, which is a daily periodic change in behavior. The most common example of circadian rhythm is what we see in Craig: the normal sleep/wake cycle in humans. We tend to get sleepy when it is dark outside and wake up when it is light outside. When this 24 hour sleep/wake cycle is interrupted, we may experience extreme tiredness or other abnormal symptoms.
Remember that all forms of innate behavior, ranging from simple reflexes (like Craig's knee jerk) to the more complex fixed action patterns (like the birds trying to find mates) are all performed correctly the first time the individual is exposed to the stimulus. Examples of these innate behaviors can be seen in a variety of animals around you.
After watching this lesson, you should be able to define behavior and innate behavior as well as identify and describe the various types of simple and complex innate behaviors.