Clark Hull's drive-reduction theory, introduced in the 1940s and 1950s and often termed the "push theory" of motivation, provides a framework for understanding how biological and learned drives influence behavior. Hull suggested that motivation originates from the need to alleviate physiological tension caused by unmet biological necessities. The theory proposes that when a basic need, such as hunger or sleep, goes unfulfilled, it creates an internal imbalance. This imbalance, or drive, pushes the organism toward behaviors aimed at restoring balance.

This theory is central to homeostasis, the body's natural tendency to maintain a stable internal environment. Homeostasis is crucial for survival, regulating temperature, hydration, and energy levels. For example, if the body's temperature increases beyond its normal range due to external factors, physiological mechanisms like sweating are triggered to dissipate excess heat. This process helps cool the body down, reducing stress and restoring internal equilibrium.

Hull's theory differentiates between two types of drives: primary and secondary. Primary drives are innate and directly linked to basic survival needs, such as hunger, thirst, and sleep. When these drives are unmet, the discomfort motivates behaviors to fulfill these needs. Secondary drives, on the other hand, are learned through conditioning and experience. These drives, such as the desire for money, social approval, or success, do not arise from biological deficits but from associations formed over time. Meeting both primary and secondary drives often results in positive reinforcement, increasing the likelihood that the behavior will be repeated.

While drive-reduction theory has significantly contributed to the study of motivation, it has faced considerable criticism. A primary critique is its inability to explain behaviors that do not directly reduce drives. For example, people often engage in activities that increase tension, such as thrill-seeking or eating when not hungry. Additionally, the theory struggles to account for the impact of secondary reinforcers like money, which do not directly satisfy biological needs but still strongly motivate behavior.