Instinct is the inborn disposition of a living organism toward a particular behavior or pattern of behaviors, characteristic of the species, and often reactions to certain environmental stimuli. Every animal species has characteristic, generally inherited patterns of responses or reactions, which they use across a wide range of environments without formal instruction, learning, or any other environmental input beyond the bare minimum for physical survival (Blakemore and Jennett 2001). Sea turtles, hatched on a beach, automatically move toward the ocean, and honeybees communicate by dance the direction of a food source, all without formal instruction.
Instinct is an innate tendency to action elicited by external stimuli, unless overridden by intelligence, which is creative and more versatile. Examples of animal behaviors that are not based upon prior experience include reproduction and feeding among insects, animal fighting, animal courtship behavior, internal escape functions, and building of nests. 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.
There is a lack of consensus on a precise definition of instinct and what human behaviors may be considered instinctual. More confining definitions argue that for a behavior to be instinctual it must be automatic, irresistible, triggered by environmental stimuli, occur in all members of a species, unmodifiable, and not require training. Based on these rigorous criteria, there is no instinctual human behavior. Likewise, some sociologists consider instincts to be innate behaviors that are present in all members of a species and cannot be overridden (Robertson 1989), but since even the drives of sex and hunger can be overridden, this definition also leads to the view that humans have no instincts. On the other hand, other individuals consider certain human behaviors to be instinctual, such as instinctive reflexes in babies (such as fanning of the toes when foot is stroked), since they are free of learning or conditioning, as well as such traits as altruism and the fight or flight response. The concept is still hotly debated.
From a religious perspective, some "psychological" instincts attributed to human beings, such as altruism, sense of "fairness" (Flam 2000), and so forth, might best be attributed to a "conscience," or to a spirit mind; that is, considered innate aspects of the human spiritual nature, rather than a purely physical phenomena. Similarly, on another level, religious or philosophical concepts may include commonly recognized instincts as part of the "physical mind" (internal character) of an animal or human, rather than the "physical body" (external form, such as part of the DNA).
It is debatable whether or not living beings are bound absolutely by instinct. Though instinct is what seems to come naturally or perhaps with heredity, general conditioning and environment surrounding a living being play a major role. Predominantly, instinct is pre-intellectual, while intuition is trans-intellectual.
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). FAPs are stereotyped behaviors that occur in a predictable, inflexible sequence in response to an identifiable stimulus from the environment. For example, at the sight of a displaced egg near the nest, the greylag goose (Anser anser) will roll the egg back to the others with its beak. If the egg is removed, the animal continues to engage in egg-rolling behavior, pulling its head back as if an imaginary egg is still being maneuvered by the underside of its beak. It will also attempt to move other egg-shaped objects, such as a golf ball, doorknob, or even an egg too large to have been laid by the goose itself (Tinbergen 1991).
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 behavioral genetics. Researchers use techniques such as inbreeding and knockout studies to separate learning and environment from genetic determination of behavioral traits.
A good example of an immediate instinct for certain types of bird is imprinting. This is the behavior that cause 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.
Instincts generally are considered external actions of the organism, and thus not behaviors such as continuous breathing, hunger, sex drive, and so forth, which are considered on a par with sight, aural ability, tactility, or taste perception.
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. 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 typically is 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. According to this proposal, 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.
The term "instinct" has had a long and varied use in psychology. In the 1870s, 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 nineteenth 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 60s and 70s, 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 one can turn to the book Instinct (1961) stemming from the 1960 conference. A number of criteria were established that distinguished 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 behaviors, 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.
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 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 response" 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 (Flam 2000).
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 (Robertson 1989), but is still hotly debated.
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