Theory of Mind is the ability to infer other persons' mental states and emotions. It is thought to have evolved as part of the human's social brain and probably emerged as an adaptive response to increasingly complex primate social interaction.
Brüne and Brüne-Cohrs (2006) explore the 'evolutionary cost' of language evolution:
This sophisticated ‘metacognitive’ ability comes at an evolutionary cost, reflected in a broad spectrum of psychopathological conditions. Extensive research into autistic spectrum disorders has revealed that theory of mind may be selectively impaired, leaving other cognitive faculties intact. Recent studies have shown that observed deficits in theory of mind task performance are part of a broad range of symptoms in schizophrenia, bipolar affective disorder, some forms of dementia, ‘psychopathy’ and in other psychiatric disorders.
Now it's fairly uncontroversial to assert that without the ability of theory of mind humans would have never evolved language (Sperber and Wilson, 2002). This is due to the fact that if one can't attribute another to have a 'mind' like ones own, or assume that other minds hold different information to ones own then one would see little point in trying to share information. (I'm sorry for the amount of 'ones' in that sentence).
Sooo, it does not seem presumptuous to assume that people interested in the evolution of language should be interested in theory of mind, in fact for many years evolutionary linguists, psychologists and biologists have been looking into this, but mostly through observing the behaviour of animals, and especially primates to see if they display theory of mind capabilities. A good summary of this work can be found here, and a lot of relevant studies can be found on this blog in the What makes humans unique? posts by Michael. I'm not going to look at the animal data in this post, but instead what the deficiencies in some human conditions can tell us about the evolution of theory of mind. That is, what can autism, schizophrenia, bipolar affective disorder, dementia, ‘psychopathy’ and other psychiatric disorders tell us?
The manifestations of impaired theory of mind are so highly diverse between and within the conditions listed this can contribute to our knowledge of theory of mind. The different components which make up theory of mind can be demonstrated by using the resource of subjects with impaired theory of mind. These subjects can be analysed using both neuroimaging and genetic methods to work out the picture step by step of the faculties that ToM is made up from.
Studies have started to compile a list of the areas of the brain which make up the neural network involved in theory of mind. Abu-Akel (2003) attempts to account for the data observed from psychiatric and developmental disorders in one neurobiological model. He lists the areas of the brain involved as follows: the frontal lobes, the Superior Temporal Sulcus (STS), the anterior cingulate cortex (ACC), and the inferior parietal cortex.
Conditions such as autism have shown us that impaired theory of mind can occur because of genetic factors from birth as well as subjects with acquired brain lesions show us that it can also be secondarily impaired in individuals who had normal theory of mind abilities prior to the event (Stuss et al., 2001)
If one was to try to pin-point some of the genes involved in theory of mind it may get infinitely more complicated than working out the neurological areas involved. I feel, however, that when the technology is available it will through looking at patients with deficits in ToM that the specific mutations will be able to be pinpointed.
I also feel that patients with deficits such as these are underused in language evolution experiments in that laboratory experiments in language evolution are often criticised for the fact that they use modern humans which doesn't tell us much about the abilities of earlier hominids. But in experiments in pragmatics people with varying abilities in ToM may be able to tell us more about the stages in which we evolved and the capabilities of early humans at these stages of evolution. This is a similar argument to that of the contributions that aphasiology can have to the field, Andreas Kyriacou did a talk at EvoLang in which he put forward the hypothesis that the biologically oldest capacities recruited for language processing are the least likely to suffer selective impairments from brain injuries as they presumably evolved pre-linguistically. Although this hypothesis is centred around capacities for grammar it would be interesting to see if it applied to the different aspects of theory of mind as well.
Abu-Akel, 2003. A neurobiological mapping of theory of mind, Brain Res. Rev. 43 , pp. 29–40.
Brüne and Brüne-Cohrs. 2006. Theory of mind—evolution, ontogeny, brain mechanisms and psychopathology. Neuroscience & Biobehavioral Reviews. Volume 30, Issue 4, Pages 437-455
Sperber and Wilson, 2002 . Pragmatics, modularity and mind-reading, Mind Lang. 17, pp. 3–23
Stuss et al., 2001. The frontal lobes are necessary for ‘theory of mind’, Brain 124, pp. 279–286.