Introversion...
An article on Yahoo News is reporting on the characters of introversion in juxtaposition to extroversion. It talks about how the extroverts seem to rule the world with there engaging mechanisms and the urge to "be someone" but that introverts seem to be better at strategic planning, thinking, memorizing.
Extroverts enjoy the external world of things, people and activities. They have more activity in brain areas involved in processing the sensory information we're bombarded with daily. Because extroverts have less internally generated brain activity, they search for more external stimuli to energize them.
So introverts need to be alone a lot to regain energy that they might have spent in the extrovert world - I would like to add that this not only affects young people. Yes and introverts behave differently and therefore are seen as strange beings in todays society. If you are a couch potato might be lying in your genes and is not connected to Introversion.