Abstract
Both speed discrimination and optic flow perception show age-related declines in performance. Given the importance of these signals for maintaining good driving, we investigated how well older adults were able to judge braking.
Participants viewed a display of dots simulating constant deceleration over a groundplane towards a visual target. Deceleration was varied from trial to trial, and participants indicated whether or not braking was sufficient to stop safely at the target.
Older adults were less likely than young adults to recognize under-braking. E.g. from an initial speed of 20 mph, they reported deceleration at only 84% of the required value to be safe on almost half the trials, whereas younger adults made this error on only one fifth of trials. Performance by older adults improved at faster speeds (errors reduced to less than 20%). There was considerable variation in performance between older individuals, with some performing nearly as well as the younger adults but others performing poorly.Both age groups tended to misjudge over-braking e.g. from 20mph, younger adults reported 125% of the required braking to be insufficient on almost 100% of trials.
There is an age-related decline in the ability to discriminate deceleration rates. This is likely to be linked to the known age-related decline in motion processing mechanisms. Given that good performance on this task also requires integrating changes in motion speed over 1-4 seconds, we suspect that age-related changes in sustained attention also play a role.