Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands (...) of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior. (Published Online November 9 2006) Key Words: adaptation; behavior genetics; Darwinian psychiatry; evolution; evolutionary genetics; evolutionary psychology; mental disorders; mutation-selection balance; psychiatric genetics; quantitative trait loci (QTL). (shrink)

Evolutionary psychiatry suggests that mental disorders can be explained in evolutionary terms (a) as failures of psychological mechanisms to produce the adaptive effects for which they were naturally selected, (b) as mismatches between naturally selected psychological mechanisms and contemporary environmental pressures, or (c) as naturally selected psychological mechanisms whose effects continue to be adaptive. In this paper, I present a philosophical critique of evolutionary psychiatry that draws on Subrena Smith’s matching problem for evolutionary psychology. For evolutionary psychiatry hypotheses to be (...) empirically supported, proponents of evolutionary psychiatry must demonstrate (1) that the contemporary psychological mechanisms involved in mental disorders resemble the psychological mechanisms of our evolutionary ancestors, (2) that the contemporary psychological mechanisms are phylogenetically descended from the ancestral psychological mechanisms, and (3) that the ancestral psychological mechanisms were naturally selected because their effects had adaptive benefits. However, for many mental disorders, evolutionary psychiatry lacks the methodological resources to demonstrate these conditions. Therefore, many evolutionary psychiatry hypotheses are empirically untestable and remain indefinitely underdetermined by data. (shrink)

This book presents comparisons of recent accounts in the formalization of natural language with informal conceptions of interaction that have been developed in both psychology and epistemology. There are four parts which explore: historical and systematic studies; the formalization of context in epistemology; the formalization of reasoning in interactive contexts in psychology; the formalization of pathological conversations. Part one discusses the Erlangen School, which proposed a logical analysis of science as well as an operational reconstruction of psychological concepts. These first (...) chapters provide epistemological and psychological insights into a conceptual reassessment of rational reconstruction from a pragmatic point of view. The second focus is on formal epistemology, where there has recently been a vigorous contribution from experts in epistemic and doxatic logics and an attempt to account for a more realistic, cognitively plausible conception of knowledge. The third part of this book examines the meeting point between logic and the human and social sciences and the fourth part focuses on research at the intersection between linguistics and psychology. Internationally renowned scholars have contributed to this volume, building on the findings and themes relevant to an interdisciplinary scientific project called DiaRaFor which was hosted by the MSH Lorraine from 2007 to 2011. (shrink)

Evolutionary psychiatrists invariably consider schizophrenia to be a paradox: how come natural selection has not yet eliminated the infamous ‘genes for schizophrenia’ if the disorder simply crushes the reproductive success of its carriers, if it has been around for thousands of years already, and if it has a uniform prevalence throughout the world? Usually, the answer is that the schizophrenic genotype is subject to some kind of balancing selection: the benefits it confers would then outbalance the obvious damage it does. (...) In this paper, however, I will show that the assumptions underlying such evolutionary accounts of schizophrenia are at least implausible, and sometimes even erroneous. First of all, I will examine some factual assumptions, in particular about schizophrenia’s impact on reproductive success, its genetics, its history, and its epidemiology. Secondly, I will take a critical look at a major philosophical assumption in evolutionary psychiatric explanations of schizophrenia. Indeed, evolutionary psychiatrists take it for granted that schizophrenia is a natural kind, i.e. a bounded and objectively real entity with discrete biological causes. My refutation of this natural kind view suggests that schizophrenia is in fact a reified umbrella concept, covering a heterogeneous group of disorders. Therefore, schizophrenia, as we now know it, simply doesn’t have an evolutionary history. (shrink)

Mental disorders are often thought to be harmful dysfunctions. Jerome Wakefield has argued that such dysfunctions should be understood as failures of naturally selected functions. This suggests, implicitly, that evolutionary biology and other Darwinian disciplines hold important information for anyone working on answering the philosophical question, 'what is a mental disorder?'. In this article, the author argues that Darwinian theory is not only relevant to the understanding of the disrupted functions, but it also sheds light on the disruption itself, as (...) well as on the harm that attends the disruption. The arguments advanced here are partially based on the view that a core feature of Darwinism is that it stresses the environmental relativity of functions and dysfunctions. These arguments show a very close empirical connection between social judgments and dysfunctions, which is of interest for psychiatric theory. Philosophically, they lead to the conclusion that the concept of mental disorder is identical to the concept of mental dysfunction. Consequently, it is both misleading and redundant to conceptualize mental disorders as 'harmful dysfunctions', and not simply as 'mental dysfunctions'. (shrink)

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also (...) exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions. (shrink)

Mental disorders are often thought to be harmful dysfunctions. Jerome Wakefield has argued that such dysfunctions should be understood as failures of naturally selected functions. This suggests, implicitly, that evolutionary biology and other Darwinian disciplines hold important information for anyone working on answering the philosophical question, ‘what is a mental disorder?’. In this article, the author argues that Darwinian theory is not only relevant to the understanding of the disrupted functions, but it also sheds light on the disruption itself, as (...) well as on the harm that attends the disruption. The arguments advanced here are partially based on the view that a core feature of Darwinism is that it stresses the environmental relativity of functions and dysfunctions. These arguments show a very close empirical connection between social judgments and dysfunctions , which is of interest for psychiatric theory. Philosophically, they lead to the conclusion that the concept of mental disorder is identical to the concept of mental dysfunction. Consequently, it is both misleading and redundant to conceptualize mental disorders as ‘harmful dysfunctions’, and not simply as ‘mental dysfunctions’. (shrink)