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The ABC of the Diametric Model, Twenty Years On

The diametric model was independently discovered by at least two authors.

As I pointed out in a recent post, what is today known as the diametric model of the mind and mental illness was stunningly anticipated by Sándor Szathmári (1897–1974) in his novel, Voyage to Kazohinia, first published in Hungarian in 1941. To the best of my knowledge, this is the earliest anticipation of the idea that autism and psychosis might be opposites—despite the author seemingly knowing nothing of autism or of the work of Hans Asperger, who was about to publish his first account of Autistichen Psychopathen im Kindesalter in wartime Austria.

Until very recently, I was in the habit of crediting Leo Kanner with having discovered autism independently, but as I mentioned in passing in a previous post, there is now damning evidence that Kanner in fact plagiarized Asperger’s original discovery. Nevertheless, there are plenty of authentic cases of independent co-discovery in the history of science: oxygen by Priestley and Scheele, the calculus by Newton and Leibnitz, and natural selection by Darwin and Wallace being but three of several cases you could cite. Another is the diametric model.

C. Badcock
Source: C. Badcock

A key implication of the model is that, if autism spectrum disorder represents an impairment in mentalism, or theory of mind, then psychotic spectrum disorder must represent its opposite: what Ahmad Abu-Akel (left), called hyper theory of mind in a paper published in 1999 and whose abstract read as follows:

The study argues that linguistic/communication dysfunctions present in disorganized schizophrenia may stem, at least in part, from an impaired theory of mind. Using pragmatics and systemic linguistic theory, the study examined speech samples of two disorganized schizophrenic patients and attempted to determine if their communicative failures are because they lack theory of mind in the sense that they do not take into account the interlocutor's mind, i.e., the interlocutor’s intentions, dispositions, and knowledge; or because they have a hyper-theory of mind through which they over-attribute mental states to their interlocutor; i.e, assume that their interlocutor has access to their intentions, dispositions and knowledge. This study indicates that disorganized schizophrenics are unlikely to be characterized as lacking a theory of mind; rather they seem to have a hyper-theory of mind, to which the psychopathological symptoms of hallucinations, delusions of reference and incoherent speech can be attributed.

Writing with Alison l. Bailey in a letter to the editor of Psychological Medicine in 2000, the diametric model of mental illness is clearly envisaged in the authors' comment that

the notion of hyper-theory of mind may have important implications for distinguishing between disorders in which a theory of mind impairment has been implicated. Specifically, hyper-theory of mind can be a useful conceptual construct in distinguishing between individuals with autism, individuals with positive symptom schizophrenia, and individuals with other schizophrenias (e.g. negative symptom schizophrenia). Furthermore, under the proposed hyper-theory of mind account, autism can be described as the retention of the reality bias beyond early childhood, whereas childhood schizophrenia can best be described as the retention of hyper-theory of mind beyond early childhood. Finally, it is our understanding that any adequate theory about a cognitive faculty not only has to be falsifiable, but has to account for the full range of observed phenomena (i.e lack, presence and excess of mentalization). We argue that the notion of hyper-theory of mind provides the additional piece to complete this range of phenomena in the domain of representational understanding of mind.

Abu-Akel’s published work did not come to my notice until Bernard Crespi and I submitted our paper entitled Psychosis and Autism as Diametrical Disorders of the Social Brain for publication in 2007, when a reviewer alerted us to it. Indeed, in the meantime Abu-Akel had not been active, and only returned to science following Crespi and I contacting him, publishing a peer review commentary on our paper and becoming one of the most notable contributors to research on the diametric model today, as several of these posts have shown.

Soon after it came out in 1995, I read Simon Baron-Cohen’s Mindblindness. In the book, Baron-Cohen cogently argued that autistics were deficient in four important respects:

  • Awareness of direction of gaze (Eye-Direction Detector, EDD)
  • Shared attention mechanism (SAM)
  • Intentionality detection (ID)
  • Theory of mind mechanism (ToMM)

It suddenly seemed absolutely obvious to me that, if autistics where deficient in these four respects, paranoid psychotics, like the famous Schreber I knew from Freud, were the exact opposite, and that their symptoms could be seen as pathological exaggerations of all four:

  • Awareness of gaze: delusions of being watched or spied on.
  • Shared attention mechanism: delusions of conspiracies.
  • Intentionality: positively as erotomania (delusions that others are in love with you) or negatively as paranoid delusions of persecution.
  • Theory of mind: delusions of reference (the belief your thoughts or actions affect things they actually can’t)/religious and mystical delusions.
C. Badcock.
Source: C. Badcock.

The last might generally be called hyper-mentalism, by contrast to the theory of mind deficits seen in autism, which you could correspondingly call hypo-mentalism. Immediately I saw all this—and it did come in one blinding, never to be forgotten moment of revelation—I began to elaborate the idea in my mind and by 1997 had included it in my lectures at The London School of Economics (left).

Finally, when at the end of the century Charles Crawford asked me to contribute to his latest book of edited chapters on evolutionary psychology, I wrote Mentalism and Mechanism: the twin modes of human cognition. Frustrated at the time it was taking for the book in which it was to appear to come out, I published it online in 2002 on The Great Debate website; and it eventually appeared in print in 2004.

Clearly, if you see hyper-mentalism/hyper-theory of mind as the key and most original concept implied by the diametric model and give due regard to precedence of publication, what is known in some quarters as the Crespi-Badcock theory should in fact be known as the ABC, or Abu-Akel, Badcock, and Crespi, theory.

At the very least, the fact that such a similar way of looking at mental illness has demonstrably occurred independently to at least three very different authors argues for it being much more than fiction or philosophy. Indeed, according to the diametric model, the model itself is the imaginary, mental component of a complete, complex whole which includes the real, mechanistic factor represented by the imprinted brain theory.

(With thanks and acknowledgement to Ahmad Abu-Akel.)


Abu-Akel, A. (1999). Impaired theory of mind in schizophrenia. Pragmatics & Cognition, 7, 247-282.

Abu-Akel, A., & Bailey, A. L. (2000). Letter to the Editor. Psychological Medicine, 30, 735-738.