Tolman developed a two-level theory of instinct in response to the debate, at the time, of the relevance of instinct to psychology. Instinct was broken down into two parts: determining or driving adjustments and subordinate acts. Adjustments are motivations or purposes behind subordinate acts, while the subordinate acts fulfill that purpose. Adjustments are the response to a stimulus and can be arranged in a hierarchy with the lowest adjustment producing subordinate acts. Subordinate acts are randomized independent actions, excluding reflexes, that are part of larger groups of activity. While considered infinitely numerous, the amount found in a grouping is limited with identifiable boundaries. The cycle begins with a stimulus that produces a determining adjustment or a hierarchy of adjustments. The lowest adjustment then cues subordinate acts that persist until the purpose of the adjustment is fulfilled.