Why might most developmental psychologists support the idea that people have some characteristics that are stable throughout their lives while other characteristics change over time? give an example.

Because children start out with the brain and the cells that they initially had. One thing that does not change is the personality you have a personality from the day you are born. The personality is the way you are when you are born and cells create your body and your mind. This is stable because it is like your chromosomes predetermined and does not change. 

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Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle

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