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5 Thinking Aloud about Mental Voices Charles Fernyhough and Simon McCarthy-Jones Abstract There is a consensus that auditory verbal hallucinations (AVHs) stem from a misattribution of inner speech to an external agency. We consider whether a developmental view of inner speech can resolve some of the problems associated with inner-speech theories. We examine neurophysiological and phenomenological evidence relevant to the issue and point up some key issues for future research. 1 Introduction The recent development of the cognitive sciences has been marked by an increased interest in inner experience. One factor in this resurgence has been the renewed legitimacy of an interest in consciousness as a topic of scientific and philosophical inquiry (e.g., Velmans & Schneider, 2007; Zelazo, Moscovitch, & Thompson, 2007). Related to this development is a growing recognition that taking consciousness seriously demands a comparable seriousness about its phenomenal properties, such as have typically been explored through introspective methods (Hurlburt & Schwitzgebel, 2007). A third factor concerns methodological advances in techniques for studying inner experience, such as the development of the method of Descriptive Experience Sampling (DES) (Hurlburt, 1990; Hurlburt & Heavey, 2006). As the science of consciousness assumes an ever more prominent position within the cognitive sciences, there is a growing consensus that any such endeavor must pay attention to the qualitative details of inner experience. One aspect of inner experience that is beginning to be studied systematically is inner speech or verbal thought (e.g., Wiley, 2006; Feigenbaum, 2009; Riley, 2004; Fernyhough, 2009). Both armchair introspection and more systematic investigations of inner experience point to it having a verbal quality. Baars (2003), for example, views inner speech as a constant of consciousness: “Overt speech takes up perhaps a tenth of the waking day; but inner speech goes on all the time” (7). A flow of verbal 88 C. Fernyhough and S. McCarthy-Jones ideation has been proposed both to have a constitutive role in conscious mentation (Carruthers, 2002) and to be a source of evidence through which we know our own minds (Carruthers, 2009). Covert mental language has been proposed to structure our cognitive environments in such a way as to augment existing cognitive capacities and expand the range of tasks that our brains can perform (Clark, 1998, 2006). Such theoretical proposals have been supported by experimental findings that disruption of covert articulatory mechanisms can impair cognitive functioning in a range of domains (e.g., Baddeley, Chincotta, & Adlam, 2001; Hermer-Vazquez, Spelke, & Katsnelson, 1999; Lidstone, Meins, & Fernyhough, 2010). Such indirect measures of inner speech use, obtained through the employment of secondary-task methodologies assumed to disrupt such speech, do not, however, allow us to distinguish between different conceptions of the phenomenon. In particular, the notion of inner speech as a stream of verbal ideation capable of describing one’s own experience and shaping new plans of action is distinctly richer than a conception of subvocal rehearsal, as inner speech has frequently been operationalized in experimental research (Jones & Fernyhough, 2007; see sec. 4 below). That said, it is likely that both conceptions of inner speech rely on common underlying cognitive and neural pathways (Al-Namlah, Fernyhough, & Meins, 2006). A further reason why inner speech has been a focus of attention concerns the role it has played in recent theorizing about hallucinations. In this chapter, we explore the idea that the study of inner speech can be illuminating about the causes of a particular kind of anomalous experience, namely, auditory verbal hallucinations (AVHs). Our contribution is in four parts. First, we set out a model of inner speech that sees it as developing through the internalization of social dialogue. We argue that this developmental view of inner speech can help to explain some of the qualitative features of the phenomenon. In the second section, we consider the experience of AVHs and attempts to account for them in terms of disordered inner speech, before going on to consider what a developmental view can contribute to such accounts of the phenomenon . In the third section, we consider implications of the developmental view for research into the neurophysiology of inner speech. Finally, we review some recent research on the phenomenology of inner speech in both voice hearers and healthy participants. 2 A Developmental View of Inner Speech Understanding where inner speech comes from, in terms of individual ontogenesis, may help us to understand the quality and behavior of this form of experience. The most informative writings in this respect are those of L. S. Vygotsky (1896–1934). Vygotsky ([1934] 1987) argued that inner speech...

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