intervening variable in psychology, a state of an organism or person postulated to explain behavior and defined in terms of its causes and effects rather than its intrinsic properties. A food drive, conceived as an intervening variable, may be defined in terms of the number of hours without food (causes) and the strength or robustness of efforts to secure it (effects) rather than in terms of hungry feeling (intrinsic property). There are at least three reasons for postulating intervening variables. First, time lapse between stimulus and behavior may be large, as when an animal eats food found hours earlier. Why didn’t the animal eat when it first discovered food? Perhaps at the time of discovery, it had already eaten, so food drive was reduced. Second, the same animal or person may act differently in the same sort of situation, as when we eat at noon one day but delay until 3 p.m. the next. Again, this may be because of variation in food drive. Third, behavior may occur in the absence of external stimulation, as when an animal forages for food. This, too, may be explained by the strength of the food drive. Intervening variables have been viewed, depending on the background theory, as convenient fictions or as psychologically real states. See also THEORETI- CAL TER. G.A.G.