Innate Behavior

Innate Behavior Definition

Let's begin by looking at the definition of innate behavior.

Innate behaviors are often automatic and occur in response to specific stimuli. Due to this, innate behaviors are highly predictable once identified within a certain species, since virtually all organisms of that species will exhibit the same innate behaviors, particularly given that some of these behaviors play an essential role in survival.

Innate behaviors are considered to be biologically determined, or instinctual.

Innate Behavior vs. Learned Behavior

Unlike innate behaviors, learned behaviors are not hardwired into the individual organism from birth and are dependent on various environmental and social factors.

There are generally accepted to be four types of learned behavior:

1. Habituation

2. Imprinting

3. Classical conditioning

4. Operant conditioning.

Habituation, which is a learned behavior that occurs when an organism ceases to react to a given stimulus the way it normally would, due to repeated exposure.

Imprinting, which is a behavior that is usually learned early in life and often involves infants and their parents.

Classical conditioning, which was made famous by Ivan Pavlov's experiments with dogs, occurs when a reaction to one stimulus becomes associated with another, unrelated stimulus due to conditioning.

Operant conditioning, which occurs when a certain behavior is reinforced or discouraged through rewards or punishments.

It is important to note that most behaviors have both innate and learned elements, but typically, one more than the other, though some may involve equal amounts of both. For example, an organism may have a genetic disposition toward exhibiting a certain behavior, but this will only occur if certain environmental conditions are met.

Types of innate behavior

There are generally considered to be four types of innate behavior:

1. Reflexes

2. Kinesis

3. Taxis

4. Fixed action patterns

Reflexes

Reflexes, also known as "reflex actions", are very simple innate behaviors that are involuntary and typically happen quickly given a specific stimulus.

In addition to the patellar reflex, another example of this sensory-motor reflex loop in your everyday life is when you withdraw your hand from a hot stove without thinking about it.

Figure 1: An illustration of the "knee-jerk reflex". Source: Vernier

Kinesis

Kinesis occurs when an organism changes the speed of its movement or turning in response to a certain stimulus (Fig. 2). For example, an organism may move faster in warmer temperatures and slower in cooler temperatures.

There are two types of kinesis: orthokinesis and klinokinesis.

• Orthokinesis occurs when an organism's speed of movement changes in response to a certain stimulus.

• Klinokinesis occurs when an organism's speed of turning changes in response to a certain stimulus.

Figure 2: The woodlouse is much more active in dry weather than moist, humid weather. Source: BioNinja

Taxis

Taxis, on the other hand, occur when an organism moves in a direction (towards or away) due to a stimulus. Three types of taxis are recognized:

1. Chemotaxis

2. Geotaxis

3. Phototaxis

Chemotaxis

Chemotaxis is a form of taxis induced by chemicals. Certain organisms will move towards specific chemicals. One unfortunate example of chemotaxis involves the movement and cell migration of tumor cells, that sense concentrations of various tumor-inducing factors, which have a vital role the development and growth of cancerous tumors.

Geotaxis

Geotaxis occurs due to the Earth's gravitational pull. Organisms that fly, such as insects, birds and bats, are involved in geotaxis, since they are utilizing the Earth's gravity to move up and down in the air.

Phototaxis

Phototaxis occurs when organisms move towards a source of light. A fine example of phototaxis would be the attraction of certain insects, such as moths, to various sources of light at night. These insects are drawn to the light source, sometimes to their detriment!

Fixed Action Patterns

Fixed action patterns are involuntary responses to stimuli that will continue to completion, regardless of the continued presence of the instigating stimuli.

Examples of Innate Behavior

Animals exhibit innate behavior in numerous ways, which can be illustrated by the following examples:

Crocodile Bite Reflex

A rather impressive and intimidating example of a reflex action would be the bite reflex of crocodilians.

All crocodilians have tiny nerve structures, called integumentary sensory organs (ISOs), on their jaws (Fig. 3). Alligators only have these organs on their jaws, while true crocodiles have them on their jaws and much of the rest of their bodies.

In fact, this is the one true way to tell the difference between a crocodile and alligator, since the variation in physical appearance between crocodiles and alligators varies throughout the world (particularly regarding crocodiles, which have a wide variation of size and head-shape).

This difference displays the extent of evolutionary divergence these two families (Alligatoridae and Crocodylidae) have experienced over the 200 million years since they last shared a common ancestor.

These ISOs are even more sensitive than human finger tips and stimulation results in an instinctive "bite" response. While a crocodilian in its natural aquatic habitat, vibrations in the water stimulate the jaws and, depending on the strength of the stimulation, may result in a bite response to catch prey (such as fish) which may be disturbing the water near its jaws.

This is why you never want to touch a crocodilians jaws! Unless they are taped shut, of course.

Figure 3: The ISOs on the jaw of a large American crocodile (Crocodylus acutus). Source: Brandon Sideleau, own work

Cockroach Orthokinesis

Perhaps you have had the unfortunate experience of having a cockroach infestation at your place of residence. In addition, perhaps you have come back to your residence at night, only to find cockroaches "out and about" in your kitchen.

Did you notice that the cockroaches quickly scatter when you turn on the lights? The cockroaches will not run in any specific direction, so long as they are running away from the light (e.g., to a place of darkness, such as under a refrigerator).

Since the cockroaches are increasing their speed of movement in response to the stimuli (the light), this is another classic example of kinesis, specifically orthokinesis, specifically phototaxis.

Innate human behavior

Lastly, let's talk about innate human behavior.

Humans are mammals and, like all other mammals, we display innate behaviors (including many of the same innate behaviors as other mammals). We've already discussed the fixed action pattern behavior of yawning, which humans and most other animals exhibit.

Can you think of any other human behaviors that may be innate? Think specifically of newborn babies.