Table 1 Key parameters of the model for an agent i.
From: The evolution of strongly-held group identities through agent-based cooperation
Parameter(s) | Description | Role in model | Subject to natural selection |
|---|---|---|---|
\(u_i, d_i, s_i\) | Rules for i’s donation based on self-comparison of potential recipient j’s reputation \(r^j\) with \(r^i\) | Governs i’s donation behaviour | Yes |
\(f_i\) | Identity fusion level for agent i | The extent to which i derives its personal identity from group G | Yes |
\(r^j\) | Donor i’s view of agent j’s reputation. When \(f_i=0\), \(r^j = r_j\). When \(f_i >0\), \(r^j = (1-f_j)r_j + f_jr_G\). | Reputation incorporating j’s representation of identity and the extent of its fusion with group G | No |
\(r_i\) | Personal reputation for an agent i | Personal identity for agent i which accrues as a consequence of i’s actions | No |
\(r_G\) | Group reputation | Group identity that is acquired by agents through their identity fusion towards G | No |
\(ctr_i\) | An additional personal reputation for fused agents capturing their support for group G | Basis for a fused agent to detect hypocrisy, given the fusion level of another agent | No |
\(n_i^{pos},n_i^{neu},n_i^{neg}\) | Number of donation actions taken by agent i that respectively: contribute to group G’s reputation; leave group G’s reputation unchanged; reduce group G’s reputation | Definition of contribution level \(ctr_i\) | No |
\(S_i\) | Probability that i plays the donation game with a randomly chosen member of the in-group. \(S_i\) fixed exogenously or \(S_i = f_i\) | Governs how well-mixed the interactions are between agents in different groups | No |
p | Probability that a fused agent i checks for hypocrisy in the potential recipient j | Allows fusion to correlate with vicarious hypocrisy, with \(p = f_i\) | No |
T | Minimum threshold on an agent’s fusion level before consideration of ostracism is invoked | Allows assessment of whether just highly fused agents can invoke fusion in the wider population | No |
