Psychophysical correlates of age-related visual decline

Much of what we know about the physical world is afforded to us by vision. With age, our ability to perceive visual information can become compromised, affecting our autonomy and quality of life. Given the rapid aging of populations worldwide, it is imperative to develop a comprehensive understanding of the effects of age on visual function. Therefore, the aim of this thesis was to use psychophysical methods to examine the effects of 'healthy' aging on visual perception, with a particular emphasis on furthering our knowledge of age-related reductions in the perception of motion. In a series of experiments, observers ranging from 18-82 years of age were tested and compared on psychophysical tasks which measured orientation and direction sensitivity, first- and second-order global motion perception, contrast sensitivity, and visual attention as measured by the Useful Field of View. Four key findings are presented within this thesis: (1) older observers demonstrate reductions in orientation and direction sensitivity that can be attributed to increased internal noise in the aged motion pathway, (2) age related impairments in global motion perception are mediated by reductions in spatial integration, (3) older female populations may be particularly susceptible to age-related impairments in motion perception, and (4) there may be a selective impairment in the processing of second-order radial motion in the aged. The results of these experiments indicate that whilst some aspects of motion processing remain preserved with age, older observers demonstrate marked impairments on a number of motion tasks.