Policy and Complex Systems
reach high values of belief or evaluation . Note also that belief is defined as a subjective probability , so the first term in the sum is restricted to the interval [ 0,1 ]. Evaluation can be either good or bad , so the second term is confined to the interval [ -1,1 ].
For subjective norm SN ( t ), we proceed in a similar fashion . However , the components are now the belief that a particular referent wishes or expects the individual to perform the behavior in question and the individual ’ s motivation to comply with that particular referent ’ s wishes . From the individual perspective each referent is part of the Pressure system , sending signals about the behavior . It follows that if a referent sends a signal regarding the behavior , then that referent wishes the individual to perform the behavior . The motivation to comply is more complicated . We therefore tie motivation to comply to the individual ’ s change in attitude AB ( t ) - AB ( t-1 ). If the individual ’ s attitude toward the behavior has increased ( i . e ., become more positive toward the behavior ), then the motivation to comply is increased . If the individual ’ s attitude has decreased , the motivation to comply is decreased . As such , SN ( t ) is computed as
In Equation ( 7 ), n r is the amount of belief reinforcement sent by referent r and
m r is the amount of reinforcement to comply with referent r . Equation ( 8 ) illustrates that increases or decreases motivation to comply based on the change in attitude toward the behavior since the last time period . The parameter determines how sensitive the individual is to changes in AB ( t ) and the parameter determines how much reinforcement of belief and motivation is required to produce a given amount of change in .
We update perceived behavioral control PB ( t ) in much the same way as AB ( t ). The Pressure and Response systems send signals about whether a particular factor is present and whether that factor facilitates or impedes the behavior in question . The only difference is that we now restrict PBC ( t ) to the interval [ 0,1 ] rather than allowing a negative component .
where c f is the amount of reinforcement that factor f is present and p f is the amount of reinforcement that factor f facilitates the behavior . Here , we have also used the same mindset parameter as in AB ( t ) to represent how much reinforcement is required to change the individual ’ s level of PBC ( t ).
The final step in making TPB dynamic is to allow for decay in the salience of all of the agent ’ s belief . Recall that they hold beliefs about outcomes being associated with the behavior , referents wishing them to perform the behavior , and factors being present that facilitate the behavior . Here we make the assumption that individuals possess some degree of inertia in changing their beliefs . That is , if an individual has a mindset that allows them to increase with relatively little reinforcement , then that individual will decay slowly . Conversely , if they require correspondingly more reinforcement for the same marginal increase they will decay faster . Essentially this means that if a person is ready to believe in something , it will be harder to convince them it is not true . On the other hand , if they are skeptical , it will require less time for the salience of recent evidence to dissipate . Thus , if the current , cumulative reinforcement value is
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