Effects of Ageing on Visual Attention and Perception

Abstract

A bilateral letter version of the spatial cueing technique introduced by Posner (1980) was employed across five experiments. Four experiments also used a perceptual cue discrimination task. In Experiment 1 the effects of ageing on visual attention and perception were examined using a simple version of the paradigm with one valid and one invalid letter (X versus T). Perceptual cue discrimination and visual orienting at both brief (150 ms) and long (500 ms) stimulus onset asynchronies (SOAs) were intact for both age-groups. In Experiment 2 however, when the same tasks were used but with an increase in complexity to four valid and four invalid letters, whilst both groups were able to accurately perform the Perception Task, older adults did not benefit from the cues when performing the Attention Task. Based on research supporting an increase in attentional set-size with categorisation of stimuli, Experiment 3 was conducted using vowels as the valid letters (A E I O). Older adults were able to successfully perform both tasks. This was interesting as the degree of visual/perceptual complexity between Experiment 2 and 3 was similar. In Experiment 4 the nature of participants' awareness of the cue-target contingencies was examined using the Experiment 1 Attention Task, however, implicit instructions were used and a post-experiment questionnaire was administered to probe awareness. Any cue-target learning that occurred in either age group was found to be explicit. In Experiment 5 electrophysiological methods were used to compare performance on the Attention and Perception tasks (using SOAs of zero & 700 ms) to explore further the dorsal/ventral distinction and age-related effects on it. The behavioural data showed strong effects of cue validity and high levels of accuracy for both age-groups as well as slower overall response times for the older adults. P1 amplitudes were greater on validly-cued trials for both groups on the Attention Task but the effect occurred later for younger adults. Within an early time window a strong dorsal/ventral distinction was present for both groups and this was maximal in the parietal lobe in the Attention Task, and in the temporal lobe in the Perception Task, which supported a dual-pathway model of vision.