How Difficult is it to Think that you Think that I Think that...? A DEL-based Computational-level Model of Theory of Mind and its Complexity
Iris van de Pol

Abstract:
Theory of Mind (ToM) is an important cognitive capacity, that is by many held to be ubiquitous in social interaction. However, at the same time, ToM seems to involve solving problems that are intractable and thus cannot be performed by humans in a (cognitively) plausible amount of time. Several cognitive scientists and philosophers have made claims about the intractability of ToM, and they argue that their particular theories of social cognition circumvent this problem of intractability. We argue that it is not clear how these claims regarding the intractability of ToM can be interpreted and/or evaluated and that a formal framework is needed to make such claims more precise. In this thesis we propose such a framework by means of a model of ToM that is based on dynamic epistemic logic. We show how the model captures an essential part of ToM and we use it to model several ToM tasks. We analyze the complexity of this model with tools from (parameterized) complexity theory: we prove that the model is PSPACE-complete and fixed-parameter tractable for certain parameters. We discuss the meaning of our results for the understanding of ToM.

Keywords: logic, computation