The Role of Inner Speech in Executive Functioning Tasks: Schizophrenia with Auditory Verbal Hallucinations and Autistic Spectrum Conditions as Case Studies

Several theories propose that one of the core functions of inner speech (IS) is to support subjects in the completion of cognitively effortful tasks, especially those involving executive functions (EF). In this paper we focus on two populations who notoriously encounter difficulties in performing EF tasks, namely, people diagnosed with schizophrenia who experience auditory verbal hallucinations (Sz-AVH) and people with autism spectrum conditions (ASC). We focus on these two populations because they represent two different ways in which IS can fail to help in EF tasks, which can be illustrative for other mental conditions. First, we review the main components of EF (see section "Executive Functions"). Then we explain the functions that IS is taken to perform in the domain of EF (see section "Inner Speech and Executive Functions") and review the evidence concerning problems about EF in the two populations of our study: Sz-AVH (see section "Executive Functions and Inner Speech in Sz-AVH") and ASC (see section "Executive Function and Inner Speech in ASC"). After this we further detail our account about what a properly functioning IS can do for both populations and how different IS profiles may impact EF performance: in the case of Sz-AVH, the uncontrolled and intrusive character of IS negatively affects EF performance, whereas in ASC, EF is not sufficiently supported by IS, given the tendency in this population to present a diminished use of IS (see section "IS in ASC and Sz-AVH: How It Relates to EF"). We finally briefly discuss Attention Deficit/Hyperactivity Disorder (ADHD) and Developmental Language Disorders (DLD) (see section "Further Considerations"). VP's research was supported by Ministerio de Ciencia, Innovacion y Universidades, postdoctoral fellowship FJC2018-036191-I. MJ's research was supported by Ministerio de Economia y Competitividad, research project FFI2016-80588-R; by Ministerio de Ciencia, Innovacion y Universidades, postdoctoral fellowship IJCI-2017-34112; and by a 2019 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation (the Foundation takes no responsibility for the opinions, statements and contents of this project, which are entirely the responsibility of its authors). This research was supported by Agencia Estatal de Investigacion, grant number: PGC2018-093464-B-I00; by the Basque Government, grant number: IT1396-19; and by the University of the Basque Country (UPV/EHU), grant number: GIU18/221.