The term instinct is generally used to explain several behavioral phenomena, such as impulsive attitudes, reflexes and a series of behaviors that are related to the automatic and spontaneous. However, from the psychological point of view, this concept was defined by the Russian scientist Ivan Pavlov as an unconditioned reflex, which is hereditary and innate. These features allow the instinct of different animal species show complex behaviors and adapted to their environment without having to be learned earlier. Among the instinctive attitudes may mention the conservation of the individual and the species, such as feeding, mating and territorial defense. Different psychological schools, maintain opposing positions regarding the existence of instinct in humans. For example, current behavioral psychologists recognize certain instinctive behaviors genetically established. For its part, Sigmund Freud defended the existence of basic instinctive forces behavior, such as the life instinct and death.
The presence of instinctive behaviors is vital because it facilitates the adaptation of different animal species to the environment.
Throughout history, many scientists established theories on instinctual behavior. Among them is William McDougall's theory, who defined instinct as an innate psychic disposition and came to set different basic instincts, such as the repulsive, the paternal, the elusive, the gregarious and so forth.