PASE

Person Acting in Several Environments

A Simulation Extending the Dynamics of Action

Developed by Virginia Blankenship

The dynamics of action is a computer simulation model and a theory of behavior developed by John Atkinson and David Birch (1970).  The simulation produces graphs showing the on-going action tendencies to engage in various activities, such as eating, drinking, and talking.  It depicts the behaviors of a single individual in a constant environment.  Each activity has an instigating force, an inhibitory force, and a consummatory force.  Although these parameter values were assumed to be related to the personality characteristics of the person and the cues within the environment, the values were chosen individually to represent relative values among the different activities.

PASE, the simulation of a person acting in several environments, posits a person with needs (e.g., need for achievement, need for power, need for affiliation) and fears (e.g., fear of failure, fear of appearing powerful, social anxiety).  Several environments (e.g., cafes, libraries, dorm rooms) either support or block the expression of those needs and fears.   Instigating forces and inhibitory forces, explained in more detail below, are derived explicitly from personality characteristics and from environmental cues in PASE.

Stream of behavior.  The Atkinson and Birch dynamics of action model conceptualized behavior as a stream.  This analogy was suggested by William James' stream of consciousness and includes the idea that what just happened affects what will happen next.  A stream of on-going behavior also implies that there are undercurrents that produce the surface behavior, undercurrents of needs and fears.  The stream analogy also focuses on the flow of behavior and allows for an analysis of behavior through time.  Behavior change marks the cessation of one behavior and the initiation of another.  This time-line of behavior puts the focus of motivation on the question of when a behavior is exhibited and for how long, aspects of behavior that can be observed and measured.

PASE also produces a stream of behavior with the added dimension of the environment in which the behavior is exhibited.  In the current simulation of PASE, five activities are possible, studying, talking, drinking, watching TV, and eating.  These activities can be expressed in three environments, a cafe, a library, and a dorm room.  The person being simulated moves from one environment to the other based on the dominant activity.   

In the cafe they can study, talk, drink cappuccinos, or eat a meal.  If they want to watch television (watching TV becomes the dominant activity), they must move to the dorm room.  In the library they can study or whisper with friends.  If they want to drink or eat, they must move to the cafe.  If they want to watch TV, they must go to the dorm room.  Finally, in the dorm room they can do all the activities except study.  (This is explained by the fact that they have a very gregarious roommate who has friends over and the TV on all the time.)  If they are in the dorm room and want to study, they must move to the library.

Instigating forces.   In the dynamics of action model, instigating forces determined the rate at which the tendency to engage in an activity, such as studying, increased over time.  An instigating force of 100 meant that the action tendency to study would increase 100 for each unit of time.  This would be represented in a graph of activities as a positively sloped line.  In PASE, the instigating force is a function of the needs of the person, the cues in the environment, and the fit between needs and the activities available.   Needs and presses are personality concepts developed by Henry Murray in his classic book, Explorations in Personality, published in 1938.  For example, studying would be highly related to a need for achievement (a characteristic of the person).  Studying would also be elicited by the library, so the library environment would have a strong (high) positive environmental press for studying.  In PASE the person's needs are multiplied by the positive environmental presses to determine an instigating force for each activity. 

A user interface allows for the personality characteristics (need for achievement, need for power, need for affiliation, need for play, and need for change) to be set.   There are five activities, as outlined in the table above, specific to three environments.  For example, talking at the cafe is comparable to whispering at the library and to chatting in the dorm room.  Talking has a stronger positive environmental press in the cafe than whispering has in the library.  The person is the same in both places; however, because of the different environmental presses, the instigating force for conversing is higher in the cafe than in the library.

Inhibitory forces.  In the dynamics of action model, inhibitory forces were negative forces that dampened and delayed the tendency to engage in an activity.  Fear of failure is an inhibitory force related to achievement activities.  A person with a high fear of failure will take longer to start studying than another person who has no fear of failure.  Fears can be set through the user interface.  Environments also have negative presses that accentuate the effects of fears.  In the dorm room, the student has a picture of his/her parents, a cue that exaggerates the fear of failure.  In the dorm room, the inhibitory force related to fear of failure and to studying is weighted highly by this high negative environmental press.  Inhibitory forces for each activity are a function of the person's fears and the negative environmental presses.

Consummatory forces.  In the dynamics of action it is assumed that an activity will not continue indefinitely because satisfaction will occur as the result of engaging in the activity.  Eating will bring about the cessation of eating.  Studying will lead to a decrease in the tendency to study and studying will be replaced by another activity.  Even watching TV will not go on forever; the tendency will decrease and be superseded by the tendency to engage in another activity.  The consummatory force of an activity is related to the nature of the activity.  Studying physics may have a higher consummatory value (and lead to a quicker end of the activity) than studying popular literature (and reading science fiction novels).   Although the consummatory value for talking might vary from one environment to another (be more satisfying in the cafe than in the library, for example), in the current version of PASE the consummatory value for a set of activities (such as talking) is the same for all three environments.

Displacement.  Instigating force from one activity can also lead to an increase in a related activity.  The instigating force to eat might also increase the tendency to drink.  This shared instigating force is called displacement and is handled in the simulation through arrays of values from 0-1.0.   The total instigating force for an activity is the instigation for that activity plus the partial instigation from all related activities.  However, full instigation is only afforded the on-going activity; the instigating force for non-dominant activities is decreased by selective attention (see below).

Substitution.  Shared consummatory force is also a part of the dynamics of action and of PASE.  Substitution is a bit more complicated than displacement, however.  Only the on-going activity has consummatory force applied to it.  Thus, only those activities that are related to the ongoing behavior will have substitute consummatory force applied to decrease the action tendency.

Consummatory lags.  The consummatory force that is applied to the on-going and dominant behavior is not applied at the instant the behavior is expressed.  Instead, a lag period, which is usually from 2-5 time units, causes a delay in decreasing the action tendency due to consummatory force.  In the dynamics of action both an initiation lag and a cessation lag was calculated.  The initiation lag delayed the on-set of consummatory force following the initiation of an activity.  (Satisfaction from eating was delayed while one chewed the food and it began to be processed by the body.)  Likewise the consummatory force continued for a time following the end of the activity.  (Satisfaction from eating continues for a while after the meal is over.)  Thus, given a lag of two time units, the activity that was dominant two time units ago receives consummatory force.  If a new activity has just become dominant, it is allowed to grow for a time without the decrease of consummation.  This causes the tendency levels of the two activities (the one going off and the one coming on) to be driven apart and avoids what was known in the dynamics of action as "behavioral chatter."

Selective attention.  Another aspect of the simulation that avoids behavioral chatter is selective attention.  Unlike the consummatory force, selective attention acts instantaneously.  The dominant activity receives 100% of its instigation, whereas the non-dominant activities receives less than 100% (usually 80%) of their instigation.  Selective attention is related to the fact that when one is engaged in an activity, the cues that support its instigation are being attended to.  The cues for those activities not being expressed are not being attended to; thus, they should have less than full instigating force applied.  Selective attention also serves to keep activities from chattering on and off, leading to clean changes in activities.

Changing Environments.  A final source of behavioral chatter, or endless loops, in the PASE simulation comes from the change in environments.  When the person is in the dorm room, for example, and studying becomes the dominant activity, that person moves to the library.  In the library the action tendencies are re-computed based on the instigating and inhibitory forces related to that environment.  It is possible that the re-calculation would result in the person moving to the cafe, for example.  At the cafe, the re-calculation could result in another move - and on and on.  An endless loop would be a strong possibility in a person with high fears and environments with high negative presses.  The high tendency that drove the person to the library to study, for example, might become negative because of a high fear of failure and strong negative environmental press in the library.  To guard against the possibility of an endless loop, the simulation has a counter that determines how many environments have been visited during each time unit.  If the person is entering the fourth environment, the simulation does not check for another move and forces the person to stay in that environment, for at least one time unit. 

The output.  Currently the output for the simulation is a graph showing the resultant action tendencies for all activities and the environment the person is in at each time unit.  The resultant action tendency at each time unit is the positive action tendency (determined by the instigating force, displacement, consummation, and substitution) minus the negative action tendency or negaction tendency (determined by the inhibitory force and force of resistance, a force that opposes the inhibitory force).  

Activate the hyperlink below to see the user interface.  You will be able to set five motives: need for achievement, need for power, need for affiliation, need for play, and need for change.  You will also be able to set five corresponding fears: fear of failure, fear of appearing powerful, social anxiety, fear of wasting time playing, and fear of change.  When you have set those values using the pull down options, click the button to change the values.  When you are satisfied with the values you have set, clock the "Continue" button to see the plot of tendencies.  The colored lines represent action tendencies.  At the bottom of the plot is a black line indicating the environment in which the person is expressing those activities.

Good luck!

PASE Simulation Model