How did Nikolaas Tinbergen explain the hierarchy of animal motivation?

In his influential work The Study of Instinct (1951), Nikolaas Tinbergen proposed that animal behavior is organized into a hierarchical mechanism. He suggested that motivational impulses from the central nervous system are channeled through successive levels of appetitive behavior, ultimately leading to a terminal, stereotyped action known as a fixed action pattern.1

Tinbergen viewed these fixed action patterns as "consummatory acts," theorizing that their performance "used up" the accumulated motivational impulses. This hierarchical structure applied to major functional categories—such as foraging, reproduction, and antipredator behavior—where each level branched into specific alternatives based on external stimuli encountered by the animal. For example, he detailed the reproductive instinct of the stickleback, where high-level behaviors like territorial fighting are further divided into specific actions like biting or chasing, depending on the rival's response.1

While historically significant, Tinbergen’s energy-based model faced criticism for its reliance on the concept of accumulating "drives," which does not accurately reflect neural transmission. Modern ethology has largely moved toward decision theory, focusing on how animals assess costs and benefits rather than the discharge of internal energy.1