"The Australian Shepherd is primarily a working dog of strong herding and guardian instincts. He is an intelligent, exceptional companion. He is versatile and easily trained: performing his assigned tasks with great style and enthusiasm. He is reserved with strangers but does not exhibit shyness. This unusually versatile stockdog works with the power and quickness to control difficult cattle as well as the ability to move sheep without unnecessary roughness. Although an aggressive, authoritative worker, viciousness toward people or animals is intolerable."  - ASCA Breed Standard.