The most advanced test for intersubjectivity in humans or other animals is designed to find out whether they can represent what others believe or know. The most common method for evaluating this capacity is the false-belief test (e.g., Gopnik & Astington, 1988; Mitchell, 1997; Perner, Leekam, & Wimmer, 1987). It is generally accepted that this capacity develops in children during their fourth year.
Wellman and Liu (2004) have argued that children can represent other persons’ diverse beliefs before they can judge false beliefs. They found that many 3-year- olds who cannot pass false-belief tests can still correctly answer a target question concerning an agent’s belief that is opposite from their own; it seems they understand that people’s actions are influenced by diverse beliefs. Language proficiency in children is correlated with their ability to pass the false-belief test (Astington & Jenkins, 1999). In particular, parental use of mental predicates in their child-directed speech is correlated with their children’s performance in false-belief tests (de Villiers & Pyers, 1997).
What is involved semantically in representing the beliefs of others, as in knowing that somebody has a false belief? Beliefs are normally expressed as propositions. So, how is the meaning of propositions related to semantic domains? One possibility is that most simple propositions express events. In Gardenfors and Warglien (2012), we modeled an event in terms of two vectors: a force vector, which typically represents an action performed by an agent, and a result vector, which describes a change in the location or properties of a patient. Consequently, the event domain is cognitively more complex than other domains.
Given this model, one may reasonably speculate that understanding the beliefs of others requires understanding their representation of events. If this conjecture is correct, it is no wonder that understanding the beliefs of others develops rather late in childhood. Consider Nelson (1996), who showed how the use of the word know develops over time in children and does not achieve its ordinary meaning until after children can pass the false-belief test.
This section has identified a number of semantic domains needed for children’s communication. Several are based on the different possible levels of intersubjectivity. I have outlined how these domains can be represented with the aid of conceptual spaces. Because independent semantic evidence suggests that the domains are necessary for modeling basic meanings, their connection to intersubjectivity can be used as a stepping stone to an analysis of the development of semantic knowledge.