The perception-action dissociation is preserved in healthy aging, but older adults rely more on contextual cues during action, potentially reflecting compensatory mechanisms to maintain visuomotor performance.
Key Findings
Results
The perception-action dissociation was preserved in both younger and older adults despite age-related changes in grasping kinematics.
Younger adults (n=25, range: 18-25 years) and older adults (n=25, range: 65-95 years) completed estimation and grasping tasks.
The Ponzo illusion influenced perceptual estimation such that objects placed on the 'far' surface were perceived as longer.
Grasping was not affected by the illusion in the same direction as perception, confirming a dissociation between the two systems.
The dissociation was maintained across both age groups despite known age-related declines in motor function.
Results
Grasping showed an effect in the opposite direction to perception in the Ponzo illusion, with larger apertures for objects placed on the 'close' surface.
In Experiment 1, two rectangular objects with varying lengths (40 mm and 42 mm) were placed on the 'far' and 'close' surfaces of a Ponzo illusion.
Perceptual estimation showed the classic Ponzo effect (objects on 'far' surface perceived as longer).
Grasping apertures were larger for objects placed on the 'close' surface of the illusion, which is the reverse of the perceptual effect.
This reversed grasping effect was observed in both younger and older adults.
Results
Background surface size, independent of illusory distance cues, modulated grasping in both age groups, with a stronger effect in older adults.
Experiment 2 removed illusory distance cues and varied only the background surface size ('big' versus 'small').
Perceptual estimations were unaffected by surface size alone in both age groups.
Grasping was modulated by surface size in both groups, indicating the reversed grasping effect from Experiment 1 was mediated by surface size rather than perceived distance.
The surface size modulation of grasping was stronger in older adults compared to younger adults.
Results
Grasping times were slower for the far surface in both age groups in Experiment 1, but this slowing was evident only in older adults in Experiment 2.
In Experiment 1 (Ponzo illusion with distance cues), both younger and older adults showed slower grasping times for objects on the 'far' surface.
In Experiment 2 (surface size only, no distance cues), the slowing effect for the larger background surface was observed exclusively in older adults.
This differential pattern suggests that older adults are more sensitive to contextual background cues during action planning and execution.
The authors interpreted this as potentially reflecting compensatory mechanisms in older adults to maintain visuomotor performance.
Results
Older adults showed age-related changes in grasping kinematics compared to younger adults.
Age-related changes in grasping kinematics were observed despite preservation of the perception-action dissociation.
Older adults demonstrated greater reliance on contextual cues during action, evidenced by stronger surface-size effects on grasping.
The authors suggested this increased contextual reliance may reflect compensatory mechanisms to maintain visuomotor performance in healthy aging.
Participants ranged from 65 to 95 years of age in the older adult group.
Background
The two visual pathways hypothesis, distinguishing vision-for-perception from vision-for-action, remains relevant in healthy aging.
The study directly tested whether the perception-action dissociation remains intact in older adults.
Prior to this study, the integrity of the dissociation in healthy aging was described as 'unclear.'
Results from both experiments supported the preservation of distinct visual processing systems for perception and action across age groups.
The findings extend the two visual pathways framework to include healthy older adults aged up to 95 years.