GSDs are one of the top 3 most intelligent dogs in the world (Border Collie is number one, Poodle is number two and GSD is number three). This is why you see so many GSDs as guard dogs and police dogs. They are very intelligent and easy to train. The average GSD can learn a new command after only 5 repetitions.
World's most intelligent dog: Border Collie. Number two: Poodle. Number three: GSD