The Measure of Madness: Philosophy of Mind, Cognitive Neuroscience, and Delusional Thought

1 The Measure of Madness

1 The Measure of Madness He was particularly distressed by the scaly appearance of his skin, which he believed was caused by a lizard growing inside his body, the lizard’s skin being evident on his arms and legs. He gave the growth of the lizard inside his chest as the reason for stabbing himself. He related this to an incident 10 years before when, in Jamaica, a lizard had run across his face. He believed the lizard had “left its mark” and that a curse had produced his skin lesions. (Browning and Jones 1988, 766) 1.1 Integrative versus Autonomous Theoretical Explanation How should we explain delusion? A constant flood of research provides information about the neural correlates of delusion at levels of resolution ranging from the molecular to the synaptic and neuroanatomical. At the same time, cognitive neuroscientists have developed information-processing theories that target the contribution to delusion of cognitive processes such as memory, perception, sensory processing, reward prediction, emotion, inference, attention, and executive functioning. Integrating all this research with the evidence gained in clinical encounters and by experimental psychologists is a project whose time is at hand. However, many theorists across the relevant disciplines argue that a fully integrative explanation is impossible. 2 Chapter 1 All we can hope for, they argue, is the accumulation of correlations between things such as the expression of genes involved in the synthesis of dopamine and glutamate, levels of activity in particular neural circuits, and the psychological features of delusion (the abnormalities of experience, belief, and behavior that bring people to clinical attention). Unfortunately, the role of philosophy in the field has been, by accident or design, to reinforce arguments that integrative explanation is impossible. This book takes a different tack. I aim to show that we can explain the contribution to delusions, like the one above, of facts like the distribution of dopamine receptors in the prefrontal cortex, as well as more familiar personallevel facts about the nature of delusional experience, thought, and behavior. We can show how facts identified and explained by disciplines operating at levels such as molecular neurobiology or neuroanatomy can explain psychological- and phenomenological -level facts that give delusion its clinical profile. In general, those who think that integrative explanation is impossible do not dispute a causal role for neurobiological and cognitive processes in psychiatric disorder. However, they argue that such causal explanations, even though they explain the mechanistic functioning of human organisms, cannot work as explanations of delusion (Bermúdez 2000; Davies 1990, 2000a,b; Bennett and Hacker 2003). The reason is that delusions are problems of personhood. Persons are organisms capable of selfawareness , conscious reflection on their own experience, and rational control of behavior (Graham 2010). Yet, so the argument goes, personal-level phenomena can only be explained in terms of other personal-level phenomena: beliefs, for example , are formed when persons try and explain their experiences using their background beliefs (Davidson 1980; McDowell 1996; The Measure of Madness 3 Thornton 2000). Personal-level explanations are theoretically autonomous according to this view. Interestingly, neuroscientists working at molecular and synaptic levels and psychiatrists and philosophers concentrating exclusively on personal-level phenomena have advocated this autonomy thesis. Equally interesting is the fact that these arguments have existed in more or less unchanged form since asylum psychiatrists in the nineteenth century attempted the intellectual project of transforming correlation to explanation for psychiatric disorder. I shall respectfully try to undermine the autonomy thesis, not by a priori refutation of arguments on which it depends, but by producing integrative explanations of some of the most intensively studied (at least by philosophers and philosophically minded cognitive psychologists) delusions over the last two decades. I shall argue that a full understanding of personallevel phenomena requires us to understand persons as complex , hierarchically organized, information-processing systems implemented in neural wetware. In fact, if we treat personallevel explanation as theoretically insulated from other forms of explanation, we lose information, not just about the brains and bodies of human organisms, but about persons themselves. The way to incorporate that information is via suitable cognitive (i.e., information-processing) theories that bridge the gap between neurobiological and personal-level explanation. Before half the potential readers close the book on the basis that existential feelings of dread, despair, or elation or the complex patterns of (ir)rational thought they initiate cannot be reduced to computational processes implemented by mechanistic functioning of the...