Priming for success: exploring the role of repetition priming in improvements in word retrieval for unimpaired speakers and people with aphasia

Aphasia is a speech and language disorder, most commonly resulting from a stroke. For many people with aphasia, finding the right word to say can be a frequent problem. However, some individuals with aphasia are able to improve their word retrieval simply by attempting to name a picture without any treatment or feedback. The first experimental chapter in this thesis (Chapter 2) explores this phenomenon, examining changes in accuracy over seven naming attempts at approximately six week intervals in a case series of 23 people with aphasia: four individuals showed significant improvement in naming, but, surprisingly, two showed performance that significantly worsened. The mechanism underpinning change in performance from repeated attempts at naming in people with aphasia has been hypothesised to be repetition priming. Hence, Chapters 3, 4 and 5 investigate parameters of repetition priming in young and older unimpaired speakers and people with aphasia. Chapter 3 explores the time course of repetition priming of picture naming in unimpaired young adults, finding significant priming with lags ranging from minutes to one month even though naming stimuli used different pictorial exemplars. There was no benefit from additional repetitions. Chapter 4 extends this to older speakers, finding no significant differences in priming from young adults, although priming was no longer significant for the older speakers at one week. Chapter 5 looks at repetition priming in people with aphasia, finding significant improvements in naming latencies with a lag of several minutes, but not at longer delays. Accuracy only showed priming with four repetitions spaced over one week. This thesis contributes to a better understanding of a mechanism underpinning treatment improvements in people with aphasia. Additionally, it provides further understanding of repetition priming mechanisms and highlights the importance of examining individual priming effects further. This will help inform both theories of word retrieval and targeted treatment for people with aphasia -- abstract.