Which of the following is NOT one of the four behavioral systems?

• A. Aggression
• B. Fear
• C. Submission
• D. Investigation

Answer: (A)

Understanding the four fundamental behavioral systems helps explain why aggression isn’t listed as one of them. These systems describe core motivational drives that organize how dogs act: curiosity and investigation drive exploration of new stimuli; play fosters social interaction and learning; fear or defensive reactions push a dog to retreat or guard itself; and submission or appeasement signals help resolve social tension with others. Aggression isn’t a separate foundational system; it’s an expression that can arise when one or more systems are highly aroused or in conflict, acting within those drives rather than standing alone. So, the options that reflect investigation, fear, and submission fit the recognized systems, while aggression does not.