Life here on the South Fork differs from many similar areas across the country in several ways, one of the most important of which is the level of sophistication in the local art scene. This extends to the performing arts, including theater, even at the nonprofessional level, as is attested to by the Center Stage at Southampton Cultural Center’s current production of “Motherhood Out Loud,” a series of scenes examining modern motherhood in America, directed by the multitalented Michael Disher.