Most of his characters and behaviours remain constant throughout his life, as outside environments do not affect his individuality in any way. His individuality is predetermined. From this standpoint, types and characteristics measured with personality are constant and even if we sharpen our wits, types and temperaments to some extent successfully, we can never change them. We do as our genes dictate. As Darwin's theory was applied to this psychological theory, it also implies that our personality connects with the secondary theory of natural selection for survival of the fittest.
Distinct personality and individual differences differentiate a person from the commonalities. One of the main personality theories, Nurture theory, connects with the Operant Conditioning of Thorndyke who talks about conditioning of man, dog or any other animal through conditioning or nurture. Every situation that is connected with the nurturing of a child till it grows up and even later as an adult produces a positive or negative reinforcement of the behaviour in the individual. Nurture theory says that every behaviour depends upon the atmosphere, circumstances, education, bringing up of a child, teachers, friends, well-wishers, neighbours, community, society, and the results of a person's behaviour are all responsible for his personality. It argues that nature or genetics, or heredity have nothing to do with the personality of the individual. Here life becomes a saga of actions and reactions.
"Thorndike's entire theory focused on behaviour at the level of simple stimulus-response events" (Neel, 1971, p.86).
Skinner applied this theory on the experiments like training an animal, through rewarding or punishing and assessing how the animal gets used to a certain behaviour, showing absolutely no signs of his hereditary behaviour, but adapting himself to an entirely new behaviour, a result of the present nurture.
There is no doubt that nurture through education, training and culture, shows a remarkable effect on the individual's make up of mind. Whatever the heredity traits and background could be, we see that army men have some common characteristics owing to their training and persisting atmosphere, where they are required to act in the best identical way possible. It is definitely possible that education, society, community, friends and teachers make a lot of difference in one's life. Most of the psychologists have approved the Nurture theory of personality.
Against the above theory, there is the Nature Theory. These are theories of personality and individual differences, trying to find out the variations between one human and another. The main target is providing psychological insights to individual personality development. In the nature theory, main stress is on the inherited genes and heredity decides all human behaviour and character of the child. His intelligence, personality and achievements are all ruled by the genetics. His DNA makes every decision for him throughout his life. There are many psychologists supporting this theory and to some extent, further studies in biology, and genetics strengthened this theory.
Through various researches, it is established by nature theorists that a large amount of our character is inheritable. Cloninger et al (1993) designed tridimensional personality questionnaires