Variety reports that CBS has greenlighted Big Brother 4 for this summer. In addition, executive producers Arnold Shapiro and Allison Grodner were given two-year contracts to oversee the production of both BB4 and Big Brother 5 -- although the network has not yet greenlighted the latter show.

Like its three predecessors, the new Big Brother will follow the same basic format, with contestants caged up in a house and booted one at a time until only one is left. However, the producers promised they would "com[e] up with new twists and turns in the game to keep it fresh and exciting and unpredictable."

The reason for the two-year contracts for Shapiro and Grodner may be the two new reality shows that they will debut within the next month: Family Business on Showtime and The Family on ABC.

Casting for Big Brother 4 will begin in mid-March, although the producers have already received around 2000 videotapes from wannabe "hamsters."