The emergence of the modern human Mind: Inner speech and its link to memory mechanisms

Inner speech (IS) is considered a unique feature of the human brain and an important component of mental life in many individuals, although it is not uniformly experienced across people.. The dysregulation of IS, in terms of its frequency, contents, or self-monitoring, has been linked to distinct neuropsychiatric conditions. In the child, more complex forms of IS usually develop around 7 years of age, when language is already well developed. While this phenomenon has usually been attributed to the maturation of verbal working memory circuits, this view does not account for the rich mental experiences and remembrances that accompany this phenomenon, which were highlighted by Lev Vygotsky's foundational studies. Addressing this issue, we propose that IS involves an engagement of two main neuronal processes: working memory capacity (especially verbal) and memory recall mechanisms, partly dependent on hippocampal function. While these two processes have long been considered as relatively separate phenomena, we will argue that there is a tight connection between working memory and episodic and semantic memory, and that this link was exploited in the human brain to amplify internal narratives, largely through the use of IS, providing structure to the human mind.