Instinctive behavior

Instinct is the inherent disposition of a living organism toward a particular behavior. Instincts are unlearned, inherited fixed action patterns of responses or reactions to certain kinds of stimuli. Innate emotions, which can be expressed in more flexible ways and learned patterns of responses, not instincts, form a basis for majority of responses to external stimuli in evolutionary higher species, while in case of highest evolved species both of them are overridden by actions based on cognitive processes with more or less intelligence and creativity or even trans-intellectual intuition.

Examples of instinctual fixed action patterns can be observed in the behavior of animals, which perform various activities (sometimes complex) that are not based upon prior experience and do not depend on emotion or learning, such as reproduction, and feeding among insects. Other examples include animal fighting, animal courtship behavior, internal escape functions, and building of nests.

Instinctual actions - in contrast to actions based on learning which is served by memory and which provides individually stored successful reactions built upon experience - have no learning curve, they are hard-wired and ready to use without learning, but do depend on maturational processes to appear.

Overview
Technically speaking, any event that initiates an instinctive behavior is termed a key stimulus (KS). Key stimuli in turn lead to innate releasing mechanisms (IRM), which in turn produce fixed action patterns (FAP). More than one key stimulus may be needed to trigger an FAP. Sensory receptor cells are critical in determining the type of FAP which is initiated. For instance, the reception of pheromones through nasal sensory receptor cells may trigger a sexual response, while the reception of a "frightening sound" through auditory sensory receptor cells may trigger a fight or flight response. The neural networks of these different sensory cells assist in integrating the signal from many receptors to determine the degree of the KS and therefore produce an appropriate degree of response. Several of these responses are determined by carefully regulated chemical messengers called hormones. The endocrine system, which is responsible for the production and transport of hormones throughout the body, is made up of many secretory glands that produce hormones and release them for transport to target organs. Specifically in vertebrates, neural control of this system is funneled through the hypothalamus to the anterior and posterior pituitary gland. Whether or not the behavioral response to a given key stimuli is either learned, genetic, or both is the center of study in the field of behavioural genetics. Researchers use techniques such as inbreeding and knockout studies to separate learning and environment from genetic determination of behavioral traits. And humans as a matter of speaking have no instincts past the early stages of infancy. Instinct should not be confused with responses that an organism is born with such as breathing, hunger, sex drive etc. These are no different than sight, aural ability, tactility or taste perception.

In a situation when two instincts contradict each other, an animal may resort to a displacement activity.

Elevators have a human-like instinct in them. They go all over the place!

Evolution
Instinctive behavior can be demonstrated across much of the broad spectrum of animal life, down to bacteria that propel themselves toward beneficial substances, and away from repellent substances. According to Darwin's theory of evolution by natural selection, a favorable trait, such as an instinct, will be selected for through competition and improved survival rate of life forms possessing the instinct. Thus, for evolutionary biology, instincts can be explained in terms of behaviors that favor survival.

A good example of an immediate instinct for certain types of bird is imprinting. This is the behaviour that causes geese to follow around the first moving object that they encounter, as it tends to be their mother. Much work was done on this concept by the psychologist Konrad Lorenz. Evolution however encourages multiple instincts, exampled by the recent case of birds in England flying east for the winter, the result being that because of global warming these birds are now surviving at very high rates, further encouraging this behavior. They return home earlier after winter, get the best breeding grounds, encouraging more breeding by them than other birds, even further encouraging this instinct.

The Baldwin Effect
In 1896, James Mark Baldwin offered up "a new factor in evolution" through which acquired characteristics could be indirectly inherited. This "new factor" was termed phenotypic plasticity: the ability of an organism to adjust to its environment during the course of its lifetime. An ability to learn is the most obvious example of phenotypic plasticity, though other examples are the ability to tan with exposure to the sun, to form a callus with exposure to abrasion, or to increase muscle strength with exercise. In addition, Baldwin pointed out that, among other things, the new factor could explain punctuated equilibria. Over time, this theory became known as the Baldwin effect.

The Baldwin effect functions in two steps. First, phenotypic plasticity allows an individual to adjust to a partially successful mutation, which might otherwise be utterly useless to the individual. If this mutation adds to inclusive fitness, it will succeed and proliferate in the population. Phenotypic plasticity is typically very costly for an individual; learning requires time and energy, and on occasion involves dangerous mistakes. Therefore there is a second step: provided enough time, evolution may find an inexorable mechanism to replace the plastic mechanism. Thus a behavior that was once learned (the first step) may in time become instinctive (the second step). At first glance, this looks identical to Lamarckian evolution, but there is no direct alteration of the genotype, based on the experience of the phenotype.

Scientific definition
The term "instincts" has had a long and varied use in psychology. In the 1870's, W. Wundt established the first psychology laboratory. At that time, psychology was primarily a branch of philosophy, but behavior became increasingly examined within the framework of the scientific method. This method has come to dominate all branches of science. While use of the scientific method led to increasingly rigorous definition of terms, by the close of the 19th century most repeated behavior was considered instinctual. In a survey of the literature at that time, one researcher chronicled 4000 human instincts, meaning someone applied the label to any behavior that was repetitive. As research became more rigorous and terms better defined, instinct as an explanation for human behavior became less common. In a conference in 1960, chaired by Frank Beach, a pioneer in comparative psychology and attended by luminaries in the field, the term was restricted in its application. During the 60's and 70's, textbooks still contained some discussion of instincts in reference to human behavior. By the year 2000, a survey of the 12 best selling textbooks in Introductory Psychology revealed only one reference to instincts, and that was in regard to Freud's referral to the "id instincts."

Any repeated behavior can be called "instinctual." As can any behavior for which there is a strong innate component. However, to distinguish behavior beyond the control of the organism from behavior that has a repetitive component we can turn to the book Instinct (1961) stemming from the 1960 conference. A number of criteria were established which distinguishes instinctual from other kinds of behavior. To be considered instinctual a behavior must a) be automatic, b) be irresistible, c) occur at some point in development, d) be triggered by some event in the environment, e) occur in every member of the species, f) be unmodifiable, and g) govern behavior for which the organism needs no training (although the organism may profit from experience and to that degree the behavior is modifiable).  The absence of one or more of these criteria indicates that the behavior is not fully instinctual.

If these criteria are used in a rigorous scientific manner, application of the term "instinct" cannot be used in reference to human behavior. When terms, such as mothering, territoriality, eating, mating, and so on, are used to denote human behavior they are seen to not meet the criteria listed above. In comparison to animal behavior such as hibernation, migration, nest building, mating and so on that are clearly instinctual, no human behavior meets the necessary criteria. In other words, under this definition, there are no human instincts.

In humans
Some sociobiologists and ethologists have attempted to comprehend human and animal social behavior in terms of instincts. Psychoanalysts have stated that instinct refers to human motivational forces (such as sex and aggression), sometimes represented as life instinct and death instinct. This use of the term motivational forces has mainly been replaced by the term instinctual drives.

Instincts in humans can also be seen in what are called instinctive reflexes. Reflexes, such as the Babinski Reflex (fanning of the toes when foot is stroked), are seen in babies and are indicative of stages of development. These reflexes can truly be considered instinctive because they are generally free of environmental influences or conditioning.

Additional human traits that have been looked at as instincts are: altruism, disgust, face perception, language acquisitions, "fight or flight" and "subjugate or be subjugated". Some experiments in human and primate societies have also come to the conclusion that a sense of fairness could be considered instinctual, with humans and apes willing to harm their own interests in protesting unfair treatment of self or others.

Other sociologists argue that humans have no instincts, defining them as a "complex pattern of behavior present in every specimen of a particular species, that is innate, and that cannot be overridden." Said sociologists argue that drives such as sex and hunger cannot be considered instincts, as they can be overridden. This definitory argument is present in many introductory sociology and biology textbooks, but is still hotly debated.