Cues, Tendencies and Actions: The Dynamics of Action revisited

The theory of the Dynamics of Action Atkinson & Birch (1970) was a theory before its time. Few psychologists of the 1970s were prepared to understand differential equations or to do computer modeling of difference equations. With modern software and computational power, the model is much easier to simulate and examine. This article describes a reparameterization of the original theory and and applies the power of simple modeling to the study of action, emotions, and social behavior. John W. Atkinson was most known for his formalization of a theory of task preference and achievement motivation Atkinson (1957, 1974, 1981). Less well known, but perhaps more important, was his work with David Birch on the Dynamics of Action (DOA) Atkinson & Birch (1970). The DOA introduced the dimension of time to the analysis of motivational strength and direction. The fundamental idea was that analysis of choice, persistence, latency, frequency and time spent can be done in a common framework: the analysis of actions over time. E.g., the initiation of an activity should be analyzed in the same manner as the persistence of an activity, for the latency of onset of an activity is equivalent to the the persistence of not doing that activity. In addition to introducing time as a variable, motivations and actions were thought to have inertial properties. This was an outgrowth of earlier work by Gestalt psychologists influenced by Kurt Lewin (e.g. Zeigarnik (1927/1967)) as well as Feather (1961) and Atkinson & Cartwright (1964). In simple terms, a wish persists until satisfied and a wish does not increase unless instigated. (This is, of course, a restatement of Newton’s 1st law of motion that a body at rest will remain at rest, a body in motion will remain in motion.) By considering motivations and actions to have inertial properties it became possible to This is a working draft of 10/10/08; comments are most welcome. email: revelle@northwestern.edu CUES, TENDENCIES AND ACTIONS:THE DYNAMICS OF ACTION REVISITED 2 model the onset, duration, and offset of activities in terms of a simple set of differential equations. Unfortunately, the theory of the Dynamics of Action was a theory before its time. Few psychologists of the 1970s were prepared to understand differential equations or to do computer modeling of difference equations. However, with a simple reparameterization (Revelle, 1986) and modern software and computational power, the model is much easier to simulate and examine. This article describes a reparameterization of the original theory and and explores the power of including temporal dyanamics in a theory of action. Applications of the revised model are extended to the dynamics of emotion (e.g., Frijda) and to social behavior. To allow the reader to explore the applications of this model, computer code simulating the revised model is written in the open source language R, (R Development Core Team, 2008) and is included in the appendix as well as on line at http://personality-project.org/r/cta.R1 The original dynamics of action The dynamics of action was a model of how instigating forces elicited action tendencies which in turn elicited actions. The basic concept was that action tendencies had inertia. That is, a wish (action tendency) would persist until satisfied and would not change without an instigating force. The consummatory strength of doing an action was thought in turn to reduce the action tendency. Forces could either be instigating or inhibitory (leading to negaction). Table 1: The basic elements of the dynamics of action Instigating Forces F Action Tendencies T Consumatory Value c Consumatory Forces C Inhibitory Forces I Negaction Tendencies N resistance Value r Force of Resistance R The relationship between instigating forces, changes in action tendencies over time, and actions was described by a simple differential equation (reminiscent of Newton’s second law) dT = F −CT (1) 1R users may source("http://personality-project.org/r/cta.R") CUES, TENDENCIES AND ACTIONS:THE DYNAMICS OF ACTION REVISITED 3 where C = cT (2) and c = 0 if an action is not being done, otherwise c is a function of the type of action (eating peanuts has a smaller c than eating chocolate cake). That is for a set of action tendencies, T, with instigating forces, F, { dTi = Fi− ciTi if Ti is ongoing dTA = FA if Ti is not ongoing (3) It is clear from equation 3 that an unexpressed but instigated action tendency will grow linearly, but once initiated will achieve an asymptotic value when the rate of growth is zero. This occurs when Fi = ciTi and thus T∞ = F/c (4)