Aim of the Present Study

The ability to attribute beliefs as well as the ability to inhibit a prepotent response are closely related. First hints towards this assumption stemmed from observations that both cognitive abilities share a common developmental timetable in childhood. Behavioral studies in children have then provided solid evidence that both concepts are indeed strongly correlated. IC is the strongest predictor for later false-belief reasoning, far above several other factors such as working memory or verbal ability (Perner & Lang, 1999). Also, training in IC abilities significantly improves false-belief performance in young children and vice versa (Kloo & Perner, 2003). A close behavioral relation between belief- reasoning and IC has been found across many different cultures (Chasiotis et al., 2007; Sabbagh et al., 2006). Furthermore, there is evidence that this close relationship persists throughout adulthood and old age. Compromised belief-reasoning in old age seems to be related to weakening IC functions (German & Hehman, 2006; McKinnon & Moscovitch, 2007). Further evidence indicating a strong connection between the attribution of beliefs and IC comes from developmental disorders with an impairment in one or both concepts. In autism, for example, a frequently observed disability to infer others’ mental states is accompanied with compromised EF abilities (Pennington & Ozonoff, 1996). Compromised IC is also one of the cardinal symptoms in ADHD. However, belief-reasoning abilities in this disorder are widely intact, suggesting a complex interaction between belief-reasoning and IC (Sodian et al., 2003).

Functional imaging and lesion studies have corroborated the view of a close relationship between IC and belief-reasoning. Lesions in the medial PFC result in an impairment of both belief attribution and IC (Rowe et al., 2001). Lesions in the left TPJ, however, seem only to have an effect on belief-reasoning (Samson et al., 2004). Functional imaging of both processes indicates an overlap of associated brain regions in medial PFC and the bilateral TPJ. This observation, however, is based on largely differing studies that have for the most part failed to scrutinize both cognitive processes in a single study. Only the results of such combined studies are suitable to test the various hypotheses regarding the nature of the belief-reasoning / IC connection. Such studies would also help to clarify whether some brain regions may qualify as specialized belief- reasoning modules. Although two previous studies have attempted such a methodological approach, only one of them (Mitchell, 2008) may have actually tapped IC. Results of this study indicate that the right TPJ, a former candidate region for a belief-reasoning module, is also engaged in other processes independent of mental state attribution. Nevertheless, this study used stimuli that differed largely across the different conditions. It is undeniable that the activation found in this study may have been due to differing stimulus properties.

Also, Mitchell’s study was unable to show IC-related activity in the medial PFC, a region frequently reported as a neural correlate of response inhibition.

The study presented in this thesis will therefore try to further clarify the connection between belief-reasoning and IC. This is done by investigating both concepts in a single study by means of a within-subjects design. Also, this study attempts to account for methodological flaws that have become apparent in previous studies. Stimuli will be used this time that only differ marginally between conditions in terms of visual properties. Also, the most commonly used task for response inhibition, a Go / No-go task, is taken to assess IC. In order to measure neural activity related to belief-reasoning, a false-belief task will be used. The false-belief task is the crucial task to measure the ability to attribute beliefs. Results from this study can help clarify the nature of the belief-reasoning / IC relationship in adulthood. However, the results stemming from this study are unable to make any assumption about this relationship in childhood or how either of these concepts influences the other during their emergence in childhood. A possible overlap between brain activity related to the two cognitive processes can indicate how closely these are related to each other. Largely overlapping areas of activation, for instance, could indicate that the ability to inhibit a response is possibly an essential component of belief-reasoning or even vice versa. Regions that are explicitly activated by belief-reasoning on the other hand could qualify as candidate regions for a belief-reasoning module. This of course would also entail clarifying the role of the right TPJ as a hypothesized belief-reasoning module. While some researchers claim that this region does indeed constitute a specific area for belief-reasoning, others have claimed that this exact region also supports other cognitive processes. Finding concurring activity for both IC and belief-reasoning in the right TPJ would contradict accounts of the right TPJ serving a specialized area for ToM reasoning.

Last but not least, this study’s results could also help replicate findings of a previous belief-reasoning study that had used a false-belief task and compared it to a true-belief task (Sommer et al., 2007). Both of Sommer et al.’s tasks were modelled according to the Sally-Anne paradigm. An almost identical approach was used in this study.

Based on previous studies investigating belief-reasoning and IC, I suggest the following hypotheses for the present study:

- Increased brain activity in the false-belief condition compared to the true-belief condition is likely to be found in the following areas: bilateral TPJ, medial PFC. This hypothesis is based on a large array of imaging studies that have found concurring activity in these areas.

- Neural correlates of IC (as reflected in the contrast No-go > Go) are likely to be located in a largely right-lateralized network consisting of the DLPFC, the bilateral TPJ and the medial PFC. Based on previous results it is suggested that medial PFC activity related to false-belief reasoning is slightly anterior to IC-related medial PFC activity.

- Resulting overlapping activity for IC and belief-reasoning is expected in areas such as the right TPJ and possibly parts of the medial PFC. This would indicate that basic processes exist that support both belief-reasoning and IC.

- In addition, it seems unlikely that the right TPJ could only be implicated in this study’s belief-reasoning condition. Based on results from previous studies, the right TPJ is likely to be implicated in this study’s IC condition as well. This could refute accounts of the right TPJ as a specialized ToM module.

- No hypotheses can be made at this point about the role of the left TPJ in both belief- reasoning and IC. Although lesion studies point to a crucial role of the left TPJ in belief- reasoning, only few imaging studies have reported activity in this area. Also, accounts of left TPJ activity during IC tasks are inconsistent across the studies reviewed here. Thus, the results from this thesis may clarify the role of the left TPJ in both IC and the attribution of beliefs.