Reasoning about diamonds, gravity and mental states: The cognitive costs of theory of mind

Reasoning about diamonds, gravity and mental states: The cognitive costs of theory of mind Ben Meijering 1 (b.meijering@rug.nl), Hedderik van Rijn 2 , Niels A. Taatgen 1 , and Rineke Verbrugge 1 Institute of Artificial Intelligence, PO Box 407 9700 AK Groningen, The Netherlands Department of Psychology, Grote Kruisstraat 2/1 NL-9712 TS Groningen Abstract Theory of mind (ToM) is required when reasoning about mental states such as knowledge, beliefs, desires, and intentions. Many complex reasoning tasks require domain- general cognitive resources such as planning, resistance to interference, and working memory. In this paper we present a study of the additional cognitive costs of reasoning about mental states. We presented participants with sequential games in which they have to reason about another player. In the so-called player condition, the other player is reasoning about the participant, whereas in the so-called balance condition, the other player is reasoning about a balance scale. Both types of games require the same comparisons, but only differ in the required depth of ToM reasoning. Games in the player condition require one additional switch between perspectives. The results show that participants make different types of mistakes in the player condition as compared to the balance condition. This finding implies a different reasoning process when reasoning about mental states. The results also show faster decreasing reaction times in the balance condition than in the player condition. Based on these findings, we argue that reasoning about mental states requires unique cognitive resources. Keywords: Theory of mind; perspective taking; decision making; sequential games; social cognition. Introduction In many social interactions we reason about one another. If, for example, our decisions or outcomes depend on someone else’s actions, we try to predict what the other will do. Predicting the other’s actions requires an understanding of how behaviors are caused by mental states such as beliefs, desires, goals, et cetera. Such an understanding is often referred to as theory of mind (Premack & Woodruff, 1978). A theory of mind, or ToM, is starting to develop around the age of three to four years (Wellman, Cross, & Watson, 2001; Wimmer & Perner, 1983). However, younger infants already are susceptible to others’ mental states (Onishi & Baillargeon, 2005). One possible explanation is that they are able to read others’ behavior, but cannot yet explicitly reason about the underlying mental states. Only after many interactions, reading many distinct behaviors, do children start to develop a theory of how behaviors generally correspond with beliefs, desires, intentions, et cetera. So far, we have introduced ToM as being a theory (Gopnik & Wellman, 1992). However, we do not want to exclude another definition of ToM that considers it to be an ability or skill to reason about mental states of oneself and others (Apperly, 2011; Leslie, Friedman, & German, 2004; Van Rij, Van Rijn, & Hendriks, 2010; Wimmer & Perner, 1983). In fact, a theory alone would not suffice when reasoning about others’ mental states. Such reasoning is an entire process of generating many possible mental state interpretations (Baker, Saxe, & Tenenbaum, 2009), and ToM reasoning might be qualitatively different from other kinds of reasoning. Some studies have shown similar but uncorrelated developmental trends in ToM tasks and non-mental tasks that require similar representations (Arslan, Hohenberger, & Verbrugge, 2012; Flobbe, Verbrugge, Hendriks, & Kramer, 2008). For example, a relative clause in the sentence “The goat that pushes the cat” requires a similar representation as the complement clause in “Alice knows that Bob is writing”, but only the complement clause requires a mental state representation. As children become older, they get better at understanding both types of sentences. However, their performance does not correlate when the factor age is controlled for. These findings show that ToM tasks might consume unique cognitive resources. It is important to note, however, that these tasks might have differed with respect to other factors, besides the aspect of mental representations. Some studies show similar performance in ToM tasks, on the one hand, and equivalent but non-mental control tasks, on the other. In the false-belief or Sally-Anne task, for example, children have to attribute a false belief about an object’s current location to Sally (Wellman et al., 2001; Wimmer & Perner, 1983). Sally stores an object at location A, but the object is moved from location A to location B while Sally is away. Therefore, Sally still thinks that the object is at location A. To pass this task, children should acknowledge that Sally falsely believes that the object is still at location A. The false-sign task is a similar but non- mental counterpart of the false-belief task. An object is first stored at location A, indicated by an arrow. Next, the object is moved from location A to location B, but the arrow still points at location A. The false sign in this task is the arrow pointing at location A, which is similar to Sally’s false belief. Children’s accuracy in both tasks is similar, and their performance correlates, even after correcting for age (Apperly, 2011; Leekam, Perner, Healey, & Sewell, 2008; Sabbagh, Xu, Carlson, Moses, & Kang, 2006). This finding implies that mental state reasoning might not qualitatively differ from other kinds of reasoning.