Social agents? A systematic review of social identity formalizations

Simulating collective decision-making and behaviour is at the heart of many agent-based models (ABMs). However, the representation of social context and its influence on an agent's behaviour remains challenging. Here, the Social Identity Approach (SIA) from social psychology offers a promising explanation, as it describes how people behave while being part of a group, how groups interact and how these interactions and ingroup norms can change over time. SIA is valuable for diverse application domains while being challenging to formalise. To address this challenge and enable modellers to learn from existing work, we take stock of ABM formalisations of SIA and present a systematic review of SIA in ABMs. Our results show a diversity of application areas and formalisations of (parts of) SIA without any converging practice towards a default formalisation. Models range from simple to (cognitively) rich, with a group of abstract models in the tradition of opinion dynamics employing SIA to specify group-based social influence. We also found some complex cognitive SIA formalisations incorporating contextual behaviour. Looking at the function of SIA in the models, representing collectives, modelling group-based social influence, and unpacking contextual behaviour stood out. Our review was also an inventory of the formalisation challenge attached to using a very promising social-psychological theory in ABMs, revealing a tendency for reference to domain-specific theories to remain vague.