The Subjective Experience of Inner Speech in Aphasia Is a Meaningful Reflection of Lexical Retrieval

Purpose: Individuals with aphasia often report that they feel able to say words in their heads, regardless of speech output ability. Here, we examine whether these subjective reports of successful "inner speech" (IS) are meaningful and test the hypothesis that they reflect lexical retrieval. Method: Participants were 53 individuals with chronic aphasia. During silent picture naming, participants reported whether or not they could say the name of each item inside their heads. Using the same items, they also completed 3 picture-based tasks that required phonological retrieval and 3 matched auditory tasks that did not. We compared participants' performance on these tasks for items they reported being able to say internally versus those they reported being unable to say internally. Then, we examined the relationship of psycholinguistic word features to self-reported IS and spoken naming accuracy. Results: Twenty-six participants reported successful IS on nearly all items, so they could not be included in the item-level analyses. These individuals performed correspondingly better than the remaining participants on tasks requiring phonological retrieval, but not on most other language measures. In the remaining group (n = 27), IS reports related item-wise to performance on tasks requiring phonological retrieval, but not to matched control tasks. Additionally, IS reports were related to 3 word characteristics associated with lexical retrieval, but not to articulatory complexity; spoken naming accuracy related to all 4 word characteristics. Six participants demonstrated evidence of unreliable IS reporting; compared with the group, they also detected fewer errors in their spoken responses and showed more severe language impairments overall. Conclusions: Self-reported IS is meaningful in many individuals with aphasia and reflects lexical phonological retrieval. These findings have potential implications for treatment planning in aphasia and for our understanding of IS in the general population.