Theory of mind impairment after right-hemisphere damage

ABSTRACT

Background: Some patients after right-hemisphere damage (RHD) show difficulty in Theory of Mind (TOM), namely, in the ability to attribute and reason about mental states of others and of themselves.

Aims: This study explored TOM abilities of individuals with right-hemisphere brain damage.

Methods & Procedures: We developed and administered a battery of TOM tasks (the aTOMia battery) to evaluate the TOM abilities of the right-hemisphere brain damaged participants in comparison to healthy control participants. The aTOMia battery included 8 types of TOM tasks.

The participants were 25 Hebrew-speakers with RHD aged 25–65 years (mean 53), 8 women and 17 men; 22 of them had a right cerebrovascular accident, and 3 were surgically treated: 2 for tumours, and 1 for cavernoma.

Outcomes & Results: The participants with RHD showed heterogeneity with respect to their TOM abilities—17 of them had TOM impairment (aTOMia), whereas 8 showed normal TOM. All patients, including the aTOMic patients, were able to use sentence embedding in their responses to the aTOMia tests items, indicating that their purely syntactic ability of embedding was intact (and did not underlie their aTOMia).

Conclusions: Individuals with RHD form a heterogeneous group. Some of them, but not all, have aTOMia. Therefore, the TOM abilities of each individual with right hemisphere should be examined. Whereas purely syntactic abilities are not affected by aTOMia, such TOM impairment may have implications for everyday life, and for the use and comprehension of language during social interaction and in understanding and conveying information.

KEYWORDS:

• Theory of mind impairment
• aTOMia
• right-hemisphere damage
• Hebrew

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1. In this paradigm, first presented by Wimmer and Perner (1983), the participants are shown a short scene acted out with puppets. First, they are shown a puppet hiding an object and then leaving the scene. Then, a different puppet enters and is seen moving the object to a different place. The first puppet re-enters the scene and the participants is asked first a control question: “Where is the object?” and then the test question: “Where will he look for the object?”. The appropriate answer to the test question is that he will search for the object in the place it was hidden first. The incorrect answer, that demonstrates immature or impaired TOM, is that he will look for the object in the place it was moved to, where it really is.

2. Notice that difficulties in assigning thematic roles in syntactically complex sentences such as relative clauses (The man that the woman kissed), like the difficulties these three case studies showed, may indeed relate to difficulty in embedding. However, they may also result from a difficulty in syntactic movement. Therefore, to directly demonstrate that TOM can be normal even when the ability to embed is impaired, it would be relevant to demonstrate a deficit in embedding in sentences without syntactic movement, such as sentences with sentential complements of verbs.

Additional information

Funding

This research was supported by the Lieselotte Adler Laboratory for Research on Child Development, by the Israel Science Foundation [grant number 1066/14, Friedmann], by the Australian Research Council Centre of Excellence for Cognition and its Disorders [CE110001021] http://www.ccd.edu.au and by a grant from the Israel Foundation Trustees (Doctoral Students Program No. 28). We would like to thank Dr. Nechama Rosenthal, Hana Karpin, and Dr. Eugenia Agronov for allowing us access to the rehabilitation centers.