In the first approximation, we can use the definition of instinct, which gave William James: "[Instinct is] the ability to act in such a way that certain objectives are achieved unexpectedly and without learning about the way of activities." Instincts are to animals and humans in order to enable them to develop, to take care of self-preservation and produce offspring.
How different species of animals having instincts is a mysterious problem, which we cannot deepen. Bergson believed instinctive activity continuation of the physiological activity of the body, as if to pre-existing complex physiological process attaches (or awakened in them) kind of "consciousness" - very vague at first, then gradually enlightens. Instinct continues to work on the organization of living matter - to the extent that it becomes difficult to distinguish where one ends and the business begins instinct. Instincts originate in the dark and an underlying region vast and uncontrolled, in the dark depths of life eludes rational definition.
It is undeniable that in man also present aspirations, which we call instinct. It is undeniable, despite discussions between McDougall, K. Lorenz and Watson, Skinner, who believe that our aspirations and motivations are determined only by training. Generally speaking, in any normal person has innate instincts or impulses preceding anyone thinking and learning disabilities and for the preservation of life, self-defense, reproduction, social hostel, basic needs. In the end, the man also is a psychological creature, and although his psyche and physiology are different from the psyche and physiology of animals, it also has a nature endowed with innate aspirations. These aspirations create the possibility of its survival, contribute to its development and conservation of the species. Person also feels the need to satisfy their needs and finds satisfaction in achieving them.
Buckley, Kerry W. Mechanical Man: “John Broadus Watson and the Beginnings of Behaviorism.” Guilford Press, 1989.
Buckley, Kerry W. "Misbehaviorism: The Case of John B. Watson's Dismissal from Johns Hopkins University". In J.T. Todd & E.K. Morris, Modern Perspectives on John B. Watson and Classical Behaviorism. Greenwood Press, 1994.
Watson, John B. “Behaviorism” (revised edition). University of Chicago Press, 1930.