Why six but not five or seven?

Where is the studies for this theory?

ok now understand what is it. After reading : http://en.wikipedia.org/wiki/Six_degrees_of_separation

But I think this is just a statistic gimmick. Cause with each contact, the span of the connection becomes bigger. By the time it gets to six, the probability of getting you connected with another person is much much higher. Therefore, this theory becomes more "probable".

It's like saying you throw a dice for six times. You call out a number you want. By the time it's six times, your chances of getting the number becomes higher.

it's all based on probability

1) the aborigine has a friend who has only one friend (that aborigine)
2) end of story