Is there a psychological explanation for the age of 18 being important in many societies? The age of eighteen is an age that in many societies gives rise to various additional rights and responsibilities.


Is there a scientific reason for assigning such right and responsibilities at the age of 18?
What are some of reasons and history for this convention?
A cursory search strongly suggests that the distinction is arbitrary and practical, with little link to developmental science.

I can find no evidence for any particularly compelling biological change centered around the age of 18.  That, along with the fact that the age of eighteen is not a universal age-of-majority, makes me say that there is no scientific basis for the choice.