3 A psychologically sound middle‐range agent‐based social simulation of collective
3.1 Conceptual model of individual decision‐making
This section proceeds as follows: In subsection 3.1.1 we present the theoretical model which is the grounding of the decision core of the ABSS. Then, subsection 3.1.2 embeds the theoretical model into the problem domain by linking it to the requirements derived in the synthesis sections of chapter 2.
3.1.1 Model description
This section defines the HAPPenInGS model (Heterogeneous Agents Providing Public Goods) of preference‐guided action selection of individuals in public good dilemmas. HAPPenInGS is specific in being grounded in the theoretic concepts and empirical results on social dilemmas and public goods, as well as in psychological theory of decision‐making. However, the model is retained as generic as possible and therefore independent of a specific case context.
Figure 5 illustrates the structural components of HAPPenInGS and their interaction. Arrows show the variables with their names and illustrate the sequence of their processing in the numbered blocks.
Block 1 represents the deduction of an investment decision based on four influencing factors
that are partly results of pre‐processing in other blocks:
The attitude towards an investment option in terms of the individual advantage the agent associates with the respective behaviour (Expected benefit of public good),
the expected conformity of an investment option with existing social norms, i.e. the subjective norm in terms of the perceived social pressure to perform or not to perform the behaviour (Expected behavioural conformity),
the expected conformity of an investment option with individual preferences regarding the distribution of investments among members of the providing group
(Expected compliance with distributional preferences), and
the perceived behavioural control regarding an investment option reflecting the availability of required opportunities and resources to perform the actual behaviour (Available investment behaviours).
While the latter factor is seen as a more or less persistent property of an individual the first three factors are dynamically adjusted based on perceptions. The processing of the perceptions is done in blocks 2 to 5.
Figure 5. Overview of the HAPPenInGS model. Arrows show the variables with their names and illustrate the sequence of their processing in the numbered blocks. See text for further explanations.
Block 2 covers the situational dimension of the public good: Individuals perceive the objective quality or quantity of the public good provided by their respective group (Perceived level of the public good) in relation to the necessity or urgency of the public good in a given external context (Perceived external relevance of the public good). The result of block 2 is a quantification of the salience of the public good in the respective context (Situational value of public good).
Block 3 relates the salience of the public good to the subjective preferences of an individual regarding the public good (Preference for public good). In the sense of the TPB this preference reflects the strength of influence that the perceived level of the public good has on the individual investment decision, e.g. high preference values in conjunction with low levels of the public good increase utility expectations for high investments. The result of the block is a measure for the expected conformity of an investment option with the modelled attitude of an agent regarding the public good (Expected benefit of public good).
Block 4 covers the formation of a subjective norm towards a behaviour. Individuals assess investment options with respect to behaviours observed in their social network (Perceived investments of others in social network). The focus is on the normative component of interpersonal social influences that entails the tendency to conform to the behavioural expectations of others (see section 2.3.2). The individual influence weight of the subjective norm is represented as a subjective preference for socially conform behaviour (Preference for social conformity). The result of the block is a measure for the expected conformity of an investment option with prevailing behaviours in the social network (Expected behavioural conformity).
Likewise, block 5 processes behaviours observable in an agent’s social context. However, in contrast to block 4 the focus is on the relation of the decision making agent’s investment option to the behaviours within his providing agent group. Here, we represent individual preferences regarding the distribution of investments within the providing group of the focal agent (Preference for distribution of investments). These preferences allow e.g. representing social orientations (see section 2.1.2.1). Egoistic or pro‐self‐preferences would e.g. favour investment options that are lower than investments chosen by other group members. Again, the output of the block is an expectation about the conformity of an investment option with the individual distributional preferences (Expected compliance with distributional preferences).
3.1.2 Compatibility of HAPPenInGS with requirements A to F
Clearly, HAPPenInGS was formulated in the light of the multi‐disciplinary scientific context laid out in chapter 2. This section is to substantiate this conceptual embeddedness of HAPPenInGS by making reference to the requirements derived in chapter 2.
Requirement A stresses the role of subjectivity of an individual in a public good dilemma. In HAPPenInGS such actor heterogeneity is represented as subjective preferences that guide individual decision‐making. The three preference dimensions covered in HAPPenInGS were purposefully chosen to enable the weighting between an attitudinal dimension (Preference for public good), a social‐normative dimension (Preference for social conformity), and a dimension representing social value orientations (Preference for distribution of investments).
While the latter preference covers an essential individual factor influencing cooperation in social dilemmas (see section 2.1.2.1), the former two preferences represent core elements of the TPB (see comments on requirement F below).
In HAPPenInGS, requirement B on spatial embeddedness is represented by the environmental context (see also Figure 2). The embedding provides the decision‐maker with local perceptions of the present state of the public good and of other (case‐specific) non‐
social external factors relevant to the decision process. Furthermore, behaviours that are put into action change the state of the environment. In addition, individuals are embedded in a non‐social temporally and spatially dynamic context as demanded by requirement D. This embedding allows perceiving the consequences of individual and collective behaviours (Level of the public good) and the generally varying temporal/spatial salience of the public good (External relevance of the public good).
Likewise, requirement C on the social embedding of decision‐making is met by HAPPenInGS.
An individual’s perception of its social context is represented by allowing individuals to relate their behaviour to the behaviour of network peers in general (Perceived investments of others in social network) or to the behaviours of others in their respective providing group (Perceived investment of other group members) in specific. In general, social exchange mechanisms other than mere observation of behaviours may become relevant, e.g. in the form of messages of social approval or disapproval sent and perceived through social network ties.
In line with requirement F, the model is psychologically sound because the core formalisation of decision‐making in HAPPenInGS is the TPB with the extension of distributional preferences. Perceived behavioural control in the sense of the TPB is represented as a fixed set of behavioural options that sets limits to an individual’s repertoire
of action. In HAPPenInGS the formation of an intention is bounded to the scope of these Available investment options. For our purposes, we assume that intentions are always put into action and translate directly to behaviour. Individual background factors are expressed by assigning subjective preference sets and by an individual’s embedding in its environments.
In principle, the operational sequence of the NAM may be reproduced in HAPPenInGS: The perception of a context that triggers a personal norm can be seen as the perception of external conditions which is evaluated to a high situational value of the public good in block 2. This evaluation would increase the expected benefit from the public good and favour high investment behaviour (as a personal norm). This expectancy might then dominate the expected behavioural conformity and compliance with distributional preferences in block 1, resulting in norm activation. Otherwise, the personal norm is deactivated.
Finally, the methodical approach of ABSS that will be outlined in section 3.2 in principle makes a significant account for requirements A to E as was detailed out in synthesis III (see section 2.2.2).
3.2 Embedding the individual: Abstract agent‐based social simulation setup