The Phenomenological Influence of Inner Speech on Executive Functions

Abstract

Inner speech is an internal verbalisation that can contribute to solving complex tasks. Variations of Inner speech and its influence on specific executive functions in typically developing adults is an area of research that is underdeveloped. This study used the Varieties of Inner Speech Questionnaire (VISQ) and split participants into high and low inner speech quality levels. Each participant completed three conditions; standard (no instruction to use or inhibit self-talk), articulatory suppression (which aims to block a person’s inner and private speech by omitting its usage) and overtly verbalising (talking out loud), to investigate the qualitative influence of inner speech on two measures of executive function. Experiment 1 (The Tower of London) showed no effect of inner speech quality levels on any of the three conditions; findings suggest that planning is not dependent upon inner speech. Experiment 2 (Card Sorting Task) indicated that lower quality levels of inner speech significantly benefited task performance; findings suggest that higher quality levels of inner speech are significantly detrimental to cognitive flexibility. These results are essential for understanding the interindividual role of inner speech quality in supporting complex executive functions. Additionally, the findings advocate that inner speech has separable trajectories for specific executive functions. Understanding the possible interactions between inner speech quality and specific executive functions could assist in maximising performance and interventions for typical and atypical populations.