Imagine that you are walking with your friend through the forest, and suddenly you find yourselves next to a bush filled with red berries. Let’s suppose that you know a lot about different plants, and you immediately recognise that these berries are not only red berries, but that they are also dangerous. In fact, they are poisonous. However, you can see the sparkle in your friend’s eyes, and that he is already reaching towards the berries to replenish his energy levels after the long walk. What do you do? Well, if you would like to save the life of your friend, or at least prevent him from an unpleasant experience, you would warn him. You would do this because you understand that he believes that these berries are good to eat, and you know that he wouldn’t go for these berries if he knew that they were dangerous.
From this example and other everyday experiences, we can see that humans possess highly sophisticated abilities to ‘read’ others’ minds. This ability, called the Theory of Mind (ToM), enables us to attribute mental states to others, and to make predictions and draw inferences from their behavior and actions to their mental states. It is therefore essential for social interactions, because it underpins our being able to effectively coordinate and communicate with others. Researchers have been investigating this ability’s characteristics for decades, and much of this research has focused on when and how it develops. In this post, I will propose that one avenue for making progress in resolving open questions about the development of ToM can be made by appealing to when we use ToM.
Since Dennett (1978) pointed out that attributing true beliefs to others cannot be empirically distinguished from agents simply making predictions about the actions of others on the basis of their own knowledge and beliefs about the world, the conventional test for ToM became probing false belief (FB) understanding. One typical way to test for the understanding of false beliefs in children is the location-change task (Wimmer & Perner 1983; Baron-Cohen, Leslie & Frith, 1985). In such a standard false belief task, participants are exposed to a story in which the main character has a false belief regarding a location of an object (as a second character changed its location while she was absent). When to explicitly indicate where the first character will look for the object, children typically fail to take into account her false belief before the age of 4, answering (or pointing) towards the new (actual) location of the object (Wimmer & Perner, 1983, Perner, Leekam & Wimmer, 1987).
There has been an ongoing debate as to whether the ability to understand others’ (false) beliefs is early developing, or whether it develops only from around the age of 4 with the emergence of other abilities, e.g. executive function and language (see for example Slade & Ruffmann, 2005). Two main lines of research have collected evidence either for or against these statements. One line of research which uses implicit measures of false-belief understanding, mostly influenced by Leslie’s theory on pretence (Leslie, 1987), suggests that infants are sensitive to others’ beliefs from very early on. For example, Onishi and Baillargeon (2005) found evidence of false-belief understanding in 15-month-olds using a violation of expectations paradigm (see Scott & Baillargeon, 2017 for a review on this research). The other line of research instead suggests that full-blown ToM develops only after the age of 4. This line of research attempts to explain positive findings with younger infants by appealing to either low level cues (e.g. Heyes, 2014), or a minimal ToM account (Apperly & Butterfill 2009) which proposes that an early developing system is rich enough to represent belief-like states only (but not beliefs per se).
How can this puzzle regarding early mind reading be solved? One may ask: if there is a conceptual change around the age of 4, then what exactly happens around that time that allows or triggers such change? I will suggest that focusing on why ToM is crucial in several aspects of our everyday social lives (from language development and communication, to cooperation and altruistic behaviour) may provide a means of answering this question.
Can the basic ability to track others’ mental states contribute to language acquisition? Some experimental evidence supports the hypothesis that, from a relatively early age, infants are sensitive to semantic incongruity. That is, they understand when an object is labelled incongruently from its real meaning (e.g. Friedrich & Friederici, 2005; 2008). A study by Forgács and colleagues (2018) investigated whether infants would track such semantic incongruities by others’ perspectives. They measured 14-months-olds event-related potential (ERP) signals, and found that infants show N400 activation (a well-established neuropsychological indicator of semantic incongruity) not only when objects are incongruently labelled from their own viewpoint, but also from their communicative partner’s point of view (see also Kutas & Federmeier, 2011; Kutas & Hillyard, 1980). These findings suggest that infants track the mental states of social partners, keep such attributed representations updated, and use them to assess others’ semantic processing. This study can further be taken as indicating that representational capacities (such as those required for belief ascription) are present at 14-month-olds in a communicative context.
Such belief attribution in similarly young infants can also be observed in ostensive-communicative inferential contexts. In a study by Tauzin and Gergely (2018), infants’ looking time was measured during the observation of unfamiliar communicative agents; children needed to interpret the turn-taking exchange of variable tone sequences, which was indicative of communicative transfer of goal relevant information from a knowledgeable to a naïve agent. In their experiments, infants observed the following interaction: one of the agents placed a ball in a certain location, and later saw the ball moving to a different location. The other agent, who had not observed the location-switch, later tried to retrieve the ball. Based on their looking times, infants only expected the ball-retrieving agent to go to where the ball really was if the first agent (who observed the location-switch) communicated the transfer. Based on these findings, the authors suggested that 13-months-old infants recognised these turn-taking exchanges as communicative information transfer, suggesting that they can attribute communication-based beliefs to other agents if they can infer the relevant information that is being transmitted.
Besides playing a role in children coming to understand important aspects of communication, ToM may play a crucial part in cooperation and altruistic behaviour. The question as to how ToM relates to, for instance, instrumental helping, has received relatively little attention. One of the first studies probing the relationship between false belief understanding and helping comes from Buttelmann, Carpenter and Tomasello (2009). During their experiments, infants observed a protagonist struggling to open a box in order to obtain a toy. In the critical part of the experiment the toy was moved by another agent from its initial box to a different box. The protagonist either observed this move, or had left the room. When the main protagonist had left the room and then tried to open the box which initially contained the toy, infants spontaneously helped him by indicating that he should try to open the alternative box instead. However, when the main protagonist observed the location-switch, infants helped him open the initial box. This suggests that by 18 months of age, helping behaviour is guided by the beliefs of the helpee. This study, amongst others (see also Matsui & Miura, 2008), support the hypothesis that representing others’ mental states is a key feature for helping and cooperating, and that infants are capable of taking into account others’ beliefs when helping spontaneously from very early on.
The ability to represent others’ mental states plays a crucial part in our social lives. Understanding what others think is important not only for high-level cooperative or competitive problem solving, but even in smaller day-to-day social interactions when we need to act fast (e.g., preventing our friends from coming to harm during a walk). The studies discussed here suggest that from a relatively early age, humans are able to adjust their helping behaviour on the basis of others’ beliefs, and the beliefs of others may shape children’s understanding of communicative episodes. Future research may do well to keep in mind that when it comes to ToM, social context seems to matter.
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