Information processing limitations with aging in the visual scaling of isometric force.

The experiment examined if age-related increases in force variability were due to decreases in visual acuity and/or visual-motor information processing deficits. Visual information scale was manipulated over a 250-fold range as young (20-29 years old) and old (60-79 years old) participants produced isometric force output to a visually presented target. Older adults were found to have a very small decrement in visual acuity, but there was no relation between visual acuity and force variability. Force variability exhibited a U-shaped trend as a function of visual information scale. Young adults had less relative variability and higher visual information transfer than the oldest old and these age differences increased with visual information scale. It is concluded that the age-related declines in visual-motor information processing influence changes in neuromuscular function and the emergent differences in force variability at the behavioral level.