The Evolution & Medicine Review

Adaptation, hyper-functional?

by Bernard Crespi

Crazy isn’t being broken or swallowing a dark secret. It’s you or me amplified

Susanna in Girl, Interrupted

Most diseases are construed as losses of function, due to mechanical, psychological or physiological breakdowns.  Many indeed are – such as heart disease, diabetes, many cancers, and disorders such as Parkinson’s or multiple sclerosis.  But might some diseases represent the opposite – extreme, pathological gains of function, or enhancements of  normally-adaptive function?  A recent study of Borderline Personality Disorder by Franzen et al. (2010) in Psychiatry Research provides evidence that this condition involves superior psychological function with regard to ‘theory of mind’, a core adaptation of human sociality.  These results, coupled with previous studies of enhanced empathy in Borderline Personality Disorder, indicate that a hyper-functioning, ‘social brain’ may be at least as psychologically maladaptive as one that is under-functional.  Some forms of ‘crazy’ may indeed represent traits of you or me, amplified.

Borderline Personality Disorder is a devastating psychiatric condition characterized by highly unstable mood, self-image, and inter-personal relationships, acute social sensitivity and intense fear of abandonment, comorbid depressive and psychotic symptoms, and an incidence of suicide hovering near ten percent (Lieb et al. 2004). The disorder was introduced to popular culture by Susanna Kaysen in her autobiographical book Girl, Interrupted, and in the eponymous film starring Winona Ryder.

A series of studies focusing on theory of mind, emotion, and empathy in Borderline Personality Disorder has generated paradoxical results: patients clearly exhibit distorted interpretations of inter-personal communication and deficits in some theory of mind tasks (e. g., Preißler et al. 2010), but they have also demonstrated, in some studies and in many anecdotal accounts, exquisite capacities to accurately read the emotional states of others. For example, Borderline patients scored higher than healthy controls on some standard tests of social-emotional abilities, such as Baron-Cohen’s “Reading the mind in the eyes” test of mentalizing and the Happé test for inferring thoughts, feelings and intentions of others in social situations (Fertuck et al. 2006; Arntz et al. 2009).

Franzen et al. (2010) have recently extended such studies to the domain of ‘exchange games’, experimental yet naturalistic social-interaction games that tap such human abilities as recognition of fairness and inference of emotional cues from facial expressions of others. In a ‘virtual trust’ game, Borderline patients proved superior to controls in their ability to attribute mental states to interaction partners when emotional cues were present. In particular, patients were less taken-in by emotional cues such as smiles that belied behavioral unfairness, suggesting enhanced skills in detecting the small, subtle, social other- and self-pretexts and deceptions that pervade human interpersonal life.  Pervade – but perhaps also harmonize and smooth, such that enhanced emotional and empathic perception may illuminate the dark shadows of human self-interest in a world that glorifies cooperation. The Franzen et al. study provides important new insights into the causes of Borderline Personality Disorder because it yields a possible solution to the Borderline Personality paradox:  hyper-developed inter-personal sensitivies may be enhanced yet maladaptive, especially when linked with emotional predispositions and fragility.

Borderline Personality disorder is unusual as one of the few psychiatric conditions strongly biased (about 3:1) towards females, a pattern that dovetails with the enhanced empathic abilities of females, compared to males, in non-clinical populations (Nettle 2007).  Moreover, among normal females ‘hyper-empathizing’ has been positively associated with measures of psychosis, suggesting that an ‘extreme female brain’ can be characterized by positive psychotic-affective traits such as paranoia and mania (Brosnan et al. 2010).  Such studies provide fundamental new data regarding the adaptive bases of human sex differences in social-brain skills – but more importantly, into the potential roles of hyper-functional human psychological adaptations in psychiatric pathology.


Arntz A, Bernstein D, Oorschot M, Schobre P.  Theory of mind in borderline and cluster-C personality disorder. J Nerv Ment Dis. 2009 197:801-7.

Brosnan M, Ashwin C, Walker I, et al. Can an ‘Extreme Female Brain’ be characterised in terms of psychosis?

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Fertuck EA, Jekal A, Song I, Wyman B, Morris MC, Wilson ST, Brodsky BS, Stanley B. Enhanced ‘Reading the Mind in the Eyes’ in borderline personality disorder compared to healthy controls. Psychol Med. 2009 39:1979-88.

Franzen N, Hagenhoff M, Baer N, Schmidt A, Mier D, Sammer G, Gallhofer B, Kirsch P, Lis S. Superior ‘theory of mind’ in borderline personality disorder: An analysis of interaction behavior in a virtual trust game. Psychiatry Res. 2010 Dec 1.

Lieb K, Zanarini MC, Schmahl C, Linehan MM, Bohus M. Borderline personality disorder. Lancet. 2004 364:453-61.

Nettle, D. Empathizing and systemizing: What are they, and what do they contribute to our understanding of psychological sex differences? British J Psychol 2007  98: 237-55.

Preißler S, Dziobek I, Ritter K, Heekeren HR, Roepke S. Social cognition in Borderline Personality Disorder: evidence for disturbed recognition of the emotions, thoughts, and Intentions of others. Front Behav Neurosci. 2010 4:182.