Hyper-mentalism: not just philosophy, visible in the brain!

Source: Front. Hum. Neurosci., 02 February 2011

The imprinted brain theory is sometimes dismissed as mere model building, and I have been disparagingly called "a philosopher rather than an experimentalist" (Nature Medicine, 16, (4) 355). But models--even philosophical ones--can in principle be tested experimentally, and this is exactly what has now been done by a group of European researchers. In a ground-breaking paper entitled, Intentional Minds, they offer "a philosophical analysis of intention tested through fMRI experiments involving people with schizophrenia, people with autism, and healthy individuals."

Citing the imprinted brain theory, the authors remind their readers that it proposes that people with autism have reduced mentalistic skills (i.e., they are "hypo-mentalistic"), while people with schizophrenia display opposite features (i.e., they are "hyper-mentalistic"). They then explain that, "Adopting a similar approach, we claim that the impairments in understanding others' intentions exhibited by paranoid patients and autistic patients, respectively, can be considered as the two extremes of a continuum."

The authors point out that the aim of their paper is to analyze how empirical research, specifically neuro-imaging studies, can address what has traditionally been thought a philosophical question: the classification of different types of intention. They distinguish between private intentions (for example, drinking something to quench your thirst), communicative intentions (you tell someone you're thirsty in the hope they will give you a drink), and prospective social intentions (you invite someone for a drink tomorrow).

The imaging study presented normal and paranoid schizophrenic subjects with cartoon-based tests depicting the various forms of intentions while scanning their brain activity. It confirmed earlier findings suggesting that the medial pre-frontal cortex (MPFC, circled in red in the illustration) is peculiarly involved in the social dimension of mentalizing but not active when it is a question of purely private intentions. Private prior intentions activated only the right temporo-parietal junction (TPJ) and the precuneus (a deeply-buried part of the parietal cortex involved with episodic memory, visuo-spatial processing, and self-awareness: the other colored area in the illustration). The left TPJ becomes active when there is a social dimension to communicating intention, but only if it relates to the present. As the authors note, the philosophical distinction between private and social intentions appears to be built into the brain as a neuro-anatomical reality.

And they found the same for the "philosophical" concept of "hyper-intentionality." In contrast to the normal subjects, the schizophrenics' intentional thinking tended to be permanently active, even when unwarranted and inappropriate: for example, in relation to inanimate objects. In other words, "patients with schizophrenia perceive agency where others see none." They also conclude that "schizophrenia patients seem unable to distinguish between intentions of others interacting and their own intentions." Taken together, this amounts to what I would call hyper-mentalism, and for the first time we can begin to see a clear picture of where it takes place in the brain. Indeed, as I have pointed out before, this insight might explain whatever real effect prefrontal lobotomy had (and it did win a Nobel Prize for its inventor): perhaps it simply disconnted the hyper-mentalizing MPFC from the rest of the brain.

Finally, the authors review the very considerable--indeed, overwhelming--evidence that the exact opposite is found in autism. Although as so often happens they did not study autistics, they predict that their model would enable researchers to distinguish between the so-called broken mirror theory of autism (which attributes autism to deficits in mirror-neurons) and the mind-blindness theory (which attributes it to mentalistic deficits). I, for one, am sure they are right and keenly await their future "philosophical/ experimental" studies.

(With thanks and acknowledgements to Bernard Crespi for bringing this study to my attention.)