SILENT STRATEGIES: INNER SPEECH AND PROBLEM SOLVING IN APHASIA

Abstract

Thesis (Ph.D.) - Indiana University, Department of Speech, Language and Hearing Sciences and the Program in Neuroscience, 2025Inner speech, the experience of “talking to yourself in your head”, plays a crucial role in cognition, communication, and self-regulation. While inner speech has been studied for nearly two centuries, its significance in clinical populations, particularly individuals with aphasia, is an emerging area of research. This dissertation explores the multifaceted nature of inner speech in both healthy aging and aphasia, examining its role in language processing, problem-solving, and psychosocial health through interdisciplinary methods. Aphasia, a language disorder most often caused by stroke, affects over two million people in the U.S., disrupting various aspects of language production and comprehension. Some individuals with aphasia report experiencing disruptions in their inner speech. This research employs multiple methodologies, including inner rhyme judgments, articulatory suppression, rating scales, questionnaires, and experience sampling, to assess inner speech at the word level, in daily life, during problem-solving tasks, and in relation to psychosocial well-being. Findings reveal that while many individuals with aphasia continue to use inner speech frequently, their inner speech is less varied in content and function compared to their neurologically healthy counterparts. In daily life, people with aphasia most often use inner speech to make decisions about food, plan activities, solve problems, and self-motivate. Experimentally, disrupting inner speech hinders improvement on complex reasoning tasks, underscoring its role in cognitive processing. Objective measures, such as inner rhyme judgment, are associated with aphasia severity and cognitive abilities like inhibition, reasoning, and problem solving, whereas subjective reports of inner speech are not. Additionally, inner speech use is linked to psychosocial health, with certain patterns, such as replaying past conversations, being associated with lower quality of life in individuals with aphasia. Overall, this dissertation provides a comprehensive perspective on inner speech, demonstrating its significance beyond language production. By integrating insights from psychology, neuroscience, linguistics, and speech-language pathology, it advances our understanding of inner speech as a critical component of cognition, communication, and well-being