Reactive aggression is commonly referred to as sharpness. However, reactive aggression must be delicately balanced in the dog's temperament because it is comprised greatly of both fight and flight instincts. Reactive aggression is only desirable if it is based on the fighting aspect with little or no trace of flight instinct being present. It is also another instinct which is not critical for Schutzhund protection training. Since social aggression has no flight counterpart, the dog does not perform under the same level of stress as in reactive aggression.
Social aggression is characterized by a dog that demonstrates a deep grumbling bark.
This type of dog also generally expresses itself in a very dominant manner. Social aggression is almost exclusively a male characteristic. Pack instinct, although not critical for Schutzhund performance, is extremely advantageous, lending itself towards high trainability. When in combination with social aggression, the advantage of social aggression is utilized while still lending the dog to a high level of trainability. Although highly important components of excellent performance temperament, the instincts described above are not the true determining factors for strong temperament.