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

Abstract

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.

Figures

Figure 1.

Task stimuli. This figure illustrates a breakdown of the stimulus lists and the tasks for which they were used. PNT = Philadelphia Naming Test; ID = identification; IS = inner speech.

Figure 2.

Day-to-day variability of scores on inner speech (IS) report and spoken naming. IS report and spoken naming tasks were administered in two 60-item sets across two testing sessions at least 10 days apart. The horizontal axis represents the difference in scores across these 2 days.

Figure 3.

Item-level performance for words reported as successful or unsuccessful inner speech (IS) across other tasks. The legend shown in Panel A applies to the entire figure. (A) Tasks relying on phonological retrieval, for which we predicted a relationship between IS report and performance. (B) Matched auditory tasks, for which we did not predict a relationship between IS report and performance. ID = identification.