Inner Speech is not so Simple: A Commentary on Cho and Wu (2013)

We welcome Cho and Wu’s suggestion that the study of auditory verbal hallucinations (AVH) could be improved by contrasting and testing more explanatory models. However, we have some worries, both about their criticisms of inner speech-based self-monitoring (ISS) models, and how explanatory their proposed spontaneous activation (SA) model is. Cho and Wu rightly point out that some phenomenological aspects of inner speech do not seem concordant with phenomenological aspects of AVH; Langdon et al. (2009) found that, while many AVHs took the third person form (‘he/she’), this was a relatively rare occurrence in inner speech, both for patients with a diagnosis of schizophrenia who experienced AVHs, and control participants. This is indeed somewhat problematic for ISS models, notwithstanding potential problems with the introspective measures used in the above study. However, Cho and Wu go on to ask: “how does inner speech in one’s own voice with its characteristic features become an AVH of, for example, the neighbour’s voice with its characteristic features?” (p. 2). Here, it seems that Cho and Wu simply assume inner speech is always experienced in one’s own voice, and are not aware of research suggesting that the presence of other people’s voices is exactly the kind of quality reported in typical inner speech. For example, McCarthy-Jones and Fernyhough (2011) have shown that it is not uncommon for healthy, non-clinical participants to report hearing other voices as part of their inner speech, as well as to report their inner speech taking on the qualities of a dialogic exchange. This is consistent with Vygotskian explanations of the internalisation of external dialogues during psychological development (Fernyhough, 2004). In this light, no ‘transformation’ from one’s own voice to that of another is needed, and no ‘additional mechanism’ needs to be added to the ISS model (McCarthy-Jones, 2012). In any case this talk of ‘transformation’ is misleading. There is no experience of inner speech first, which is somehow then transformed. The question about whether inner speech is implicated in AVHs is about whether elements involved in the production of inner speech experiences are also involved in the production of some AVHs. There seems to be fairly strong evidence to support this. That inner speech involves motoric elements has been empirically supported by several electromyographical (EMG) studies (e.g. Jacobsen, 1931). Later experiments made the connection between inner speech and AVH, showing that similar muscular activation is involved in AVH (Gould 1948,