Energy models of motivation: A reconsideration

During the first half of the 20th century, most theories of behavior invoked some concept of motivation that included an energy or drive variable. For a variety of reasons, such variables were widely criticized and have been generally out of fashion during the past 30 years. This paper examines some of the criticisms of energy variables, especially as postulated by Lorenz, and suggests ways of overcoming many of the objections raised. An energy variable is proposed that has multiple sources of energy (both internal and external) and multiple means of dissipating energy (performance of the behavior, performance of alternative behavior, and passage of time). Results from studies on dustbathing in chickens, attack and other behavior in fish, and sleep in humans are reviewed and shown to be partially accounted for by fluctuations in an energy variable. In most cases, however, an additional variable, called threshold, is required for a full account of the observed behavior. It is concluded that a general theory of motivation should include both an energy variable and a threshold variable. (C) 1997 Elsevier Science B.V.