This dissertation explores how listeners extract meaning from personal and reflexive pronouns in spoken language. To be understood, words like her and herself must be linked to a prior element in the speech stream (or antecedent). This process draws on syntactic knowledge and verbal working memory processes. I present two original research studies investigating moment-to-moment sentence processing and final comprehension of sentences containing proforms in children and adults with and without language impairments. Chapter 2 provides an overview of syntactic constraints and psycholinguistic evidence from unimpaired listeners in addition to an introduction to the language impaired populations. Chapter 3 reviews psycholinguistic evidence of similarity-based interference in verbal working memory during unimpaired language processing before presenting a recent account — the Intervener Hypothesis — that points to similaritybased interference as a source of processing and comprehension difficulty in language impaired populations. Chapter 4 presents a series of experiments in children with typical language development (TLD) and children with a developmental language impairment — specific language impairment (SLI). The processing patterns of the two participants groups reveal qualitative differences and children with SLI demonstrate increased comprehension difficulty relative to TLD children. Chapter 5 presents a series of experiments in adults with an acquired language impairment — agrammatic Broca's aphasia — and age-matched control participants. Results reveal increased processing and comprehension difficulty of sentences containing pronouns relative to reflexives for individuals with Broca's aphasia. The processing patterns demonstrated by unimpaired child and adult participants reveal a number of striking similarities. In addition, the processing patterns of children with SLI mirror those of adults with Broca's aphasia. Although the etiology of language impairments differs in these groups, children with SLI and adults with Broca's aphasia share many of the same language processing difficulties. As such, I evaluate the potential of a single theoretical framework (the Intervener Hypothesis) to account for the patterns observed in each group. In addition, I evaluate how processing and comprehension patterns change across the lifespan in participants with unimpaired language and the extent to which processing and comprehension patterns overlap.