Abstract
Oculomotor functions are established surrogate measures of visual attention shifting and rate of information processing, however, the temporal characteristics of saccades and fixations have seldom been compared in healthy educated samples of younger and older adults. Thus, the current study aimed to compare duration of eye movement components in younger (18–25 years) and older (50–81 years) adults during text reading and during object/alphanumeric Rapid Automatic Naming (RAN) tasks. The current study also aimed to examine the contribution of oculomotor functions to threshold time needed for accurate performance on visually-driven cognitive tasks (Inspection Time [IT] and Change Detection [CD]). Results showed that younger adults fixated on individual stimuli for significantly longer than the older participants, while older adults demonstrated significantly longer saccade durations than the younger group. Results also demonstrated that older adults required longer threshold durations (i.e., performed slower) on the visually-driven cognitive tasks, however, the age-group time difference on the CD task was eradicated when the effects of saccade duration were covaried. Thus, these results suggest that age-related cognitive decline is also related to increased duration of saccades and hence, highlights the need to dissociate the age-related motor constraints on the temporal aspects of oculomotor function from visuo-cognitive speed of processing.
Highlights
Most human behaviour is visually driven[1], with visual attention considered the key driver of most perceptual, cognitive, and behavioural processes[2,3,4]
In regard to statistically controlling the effect of oculomotor function from performance on visuo-cognitive tasks, we predicted that doing so would decrease the age-group variance seen on the Change Detection (CD), but not on the Inspection Time (IT), due to the CD tasks requirement for rapid eye movements
Correlation analyses in the current study revealed a significant positive correlation between IT threshold exposure duration and Rapid Automatic Naming (RAN) Numbers naming score for older adults, this did not entirely support our hypothesis and highlighted the fact that the ‘number of items named in 60 seconds’ may not be entirely reflective of efficient visual processing alone
Summary
Most human behaviour is visually driven[1], with visual attention considered the key driver of most perceptual, cognitive, and behavioural processes[2,3,4]. Visual tracking performance (positional precision and smooth pursuit velocity gain of visual tracking) has shown similar age related effects[44], while anti-saccade paradigms (saccade in the opposite direction of a visual target) have demonstrated both reduced inhibitory control and reduced motor speed[43,45], which is in line with theories of cognitive aging including the Inhibitory Deficit Hypothesis[46] This hypothesis suggests that older adults are more susceptible to task-irrelevant stimuli and have greater difficulty inhibiting distractions, resulting in heightened distractibility, reduced working memory capacity, and greater proactive interference[46]. It was hypothesized that performance on the visuo-cognitive tasks (IT and CD) would significantly predict RAN naming and reading scores, given that the IT and CD are widely accepted measures of visual processing speed and visual short-term memory capacity[10,54]
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