@Leona/ Bwenyeye - you have just stepped into the realm of the famous Nature-Nurture Controversy in psychology.
It is akin to asking: 'of which, nature or nurture, contributes more to an individual's personality? Or, which contributes more to the area of a rectangle, its length or its width?"
So its main thrust is: Are an individual's behavioural traits innate/ inborn qualities (thus nature) or are they shaped i.e nurtured, by the environment (parents, personal experiences,etc)?
Was Paul Tergat born an athlete or he learnt/ trained to be a world-class athlete?
If you believe in nature, then your behavioural traits were already programmed into your genes zamani n there's precious little you can do to change that behaviour - kama wewe ni mwizi, bad temper,lazy it is irreversible so get used to it!
Conversely, if you believe an individual's behavioural traits are learned and shaped by the environment then a person's behaviour can be changed. It means as babies they start on a clean slate (called tabula rasa) which gets filled up/moulded as time and experiences are accumulated to make up an individuals personality.
http://en.wikipedia.org/...i/Nature_versus_nurture
http://findarticles.com/.../is_0002/ai_2699000233/