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subjective
benefit of the
public good
. As a second dimension, the expected
social
conformity
of an investment option with existing social norms is represented. This
dimension covers the influence of “injunctive social norms” [11]. In general, “thick
network(s) of social interactions” [12] can yield social coordination [13, 14] which in
turn helps to overcome social dilemmas. The essential understanding is that individu-
als possess and utilise social knowledge in social dilemma situations [15]. Finally, we
represent social value orientations as a preference for a desired ratio between the deci-
sion-maker's contribution to the public good and the contributions of the other mem-
bers of the providing group. This representation of an expected conformity of an
investment option with a desired
distribution of investments
accounts for the concept
of social value orientations or social motives [16, 17], which are essential individual
factor influencing cooperation in social dilemmas [18].
In HAPPenInGS the evaluation of the preference dimensions is based on an indi-
vidual's perception of its situational context. The environmental sub context provides
the decision-maker with local and subjective perceptions of the present state of the
public good and of other (case-specific) non-social external factors relevant to the
decision process. Behaviours that are put into action change the state of the environ-
ment. The actor perceives the consequences of his and collective behaviours as well
as the generally varying temporal/spatial salience of the public good. This perception
process constructs the actor's internal representation of the expected benefit of the
public good. In its social context an individual perceives the investment behaviours of
its social network peers and actively constructs an internal representation of the (pre-
sent) social norm. Furthermore, the individual perceives the investment behaviours of
other members of its providing group. This perception is not evaluated in a behav-
ioural normative sense. Instead the individual compares the perception to its own
investment behaviour and evaluates the situation with respect to its social value
orientations.
3
Embedding the Individual: Agent-Based Model Setup
The agent's environment context has a grid topology. Some of the patches are popu-
lated by agent groups of a fixed size n. In each simulation step the level of the public
good on a group's patch is calculated from the contributions of the group members.
An agent's investment state variable x is one of 11 distinct behavioural options that
reflect investments of 0.0, 0.1 up to 1.0 in steps of 0.1. Based on the contributions of
the n agents we determine the level of the generated public good from a logistic curve
describing production function of the public good. For low individual investments x
i
the value is close to 0. For high values of x
i
(for all i) it approaches 1.0. As for the
success of the public good provision only the sum of the investments of all group
members is crucial, unequally distributed contributions may yield identical success.
This allows cases of free riding to occur e.g. if substantial levels of the public good
were provided by a majority of group members and a minority refuses to invest. Fur-
thermore, patches vary in the success of the public good provision by the local agent
group. Other spatial relations or dynamics are not considered in the abstract model.
