Richard Solomon and his associates (1980; Solomon & Corbit, 1974) developed the opponent-process theory, which offers another explanation for this effect. The theory suggests that each state or emotion that we experience triggers a force to experience the opposite state. For example, happiness generates its opposite, unhappiness; fear generates its opposite, elation, and so on. The effect of these opponents is to dampen the intensity and length of time that we experience any emotional state, and to increase the likelihood that we will experience the opposite emotional state. Mook (1987) argues that this is very adaptive because it is potentially dangerous for us to be in any emotional state (elation or depression) for too long a time.