In this dissertation I examine language functioning in healthy young and older adults, and patients with unilateral brain-damage by measuring the effects of repeated practice on naming latencies for a set of pictured objects, and examining the ability to use prosody (the melody of speech) to aid in comprehension of syntax and affect. Chapter 1 provides a review of matters relating to speech production and comprehension, aging, and hemispheric differences that are relevant to the experiments presented here. In Chapter 2, I investigate a unique case of speech production, confrontation naming, and the effects of repeated practice. Although these data show that older adults take longer to name an object than young adults, of primary interest is that aphasic patients fail to show the progressive latency reduction or the progressive reduction in variability seen for the controls. These data support the idea that successful naming by aphasic patients may come about by different underlying operations - failing to reactivate the same neural circuits from one occasion to the next.

In chapters 3 and 4, I examine the role of individual prosodic components for syntactic and affective speech comprehension. The data reveal that young and older adults exhibit a task-dependent hierarchy. That is, when the task involves correctly parsing sentences, the most important feature is timing-variation, and when the task is to either perform a similar task at the single-word level or correctly identify the emotional tone of the speaker, the most important feature is pitch-variation. However, the right-hemisphere brain-damaged patients show a clear loss in sensitivity for pitch variation.

Taken together, the data from these experiments reiterate the findings in the aging literature that language functioning is well preserved in old age, despite some general slowing and added inefficiencies when the task difficulty increases. Furthermore, these studies provide insights into the variable findings regarding aphasic patient naming, as well as an important role of the right hemisphere for speech comprehension.