A meaningful social life relies on understanding others’ minds and behaviours. Theory of mind (ToM) is the ability to reason about an individual’s mental states such as beliefs and desires, and to understand and predict how these mental states shape an individual’s behaviour. This thesis aims to develop a systematic approach for understanding the underlying processes of a simple theory of mind and to evaluate the performance of theory of mind ability in a social context. For this purpose, two case studies using agent-based modelling methodology has been conducted. An original set of basic processes underpinning ToM ability, termed Belief Representation Systematic Approach (BRSA) has been explored through these two models. BRSA reconstructs ToM processes into four main phases: Perception, Memory, Reasoning beliefs and desires, and Action. BRSA clarifies that there is a difference between having ToM and ‘using’ it. The reasoning involved in the third and fourth phases of BRSA influences the agents’ performances. BRSA shows that false belief tasks require two preconditions, resources and reasoning, to be considered as an acid test for ToM competence. Both models demonstrate that developing agents’ understanding of others’ mental states on the micro level will lead to significant improvements in their social performances on the macro level.