Instinct is the inherent disposition of a living organism toward a particular behavior. Instincts are generally inherited patterns of responses or reactions to certain kinds of stimuli. Instinct provides a response to external stimuli, which moves an organism to action, unless overridden by intelligence, which is creative and more versatile. Since instincts take generations to adapt, an intermediate position, or basis for action, is served by memory, which provides individually stored successful reactions built upon experience. The particular actions performed may be influenced by learning, environment and natural principles. Generally, the term instinct is not used to describe an existing condition or established state.
Examples can more frequently be observed in the behavior of animals, which perform various activities (sometimes complex) that are not based upon prior experience, such as reproduction, and feeding among insects. Other examples include animal fighting, animal courtship behavior, internal escape functions, and building of nests.
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.

Evolution
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.

The Baldwin Effect

Definitions
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

Maladaptivity
Biological Imperative
Organism
Nature
Psychological nativism