Abstract:

Sensory function is considered a basic resource for the aging of cognition. According to the information- degradation hypothesis (Schneider & Pichora-Fuller, 2000), the decline of sensory function reduces the input of peripheral stimulating information to the central neural system of older adults, and so more attention resources are demanded to process the limited quality sensory information. With the result of fewer resources being left for cognitive processing, older adults have worse cognitive performance than younger adults. The present study adopted a 2 (age: old and young) × 4 (visual perceptual stress: high, medium, low, no-noise) mixed design, with age as a between–subject variable and visual perceptual stress as a within-subject variable, to examine the role of visual function on cognitive aging. Three primary mental abilities (PMA), spatial orientation ability, numerical ability and inductive reasoning ability, were used as the indexes of cognitive functions. All cognitive tests were displayed under four different levels of visual perceptual stress by standardized programs on the computer. The visual perceptual stress was created by covering stimuli with Gaussian noise. Notably, the visual perceptual stress of each subject was determined by the condition of each individual. Therefore, all participants undertook equal visual perceptual stress towards task–related stimuli in each stress condition. It was expected that the age–related differences would decrease significantly or disappear completely when the older and younger participants undertook the same level of visual perceptual press. Thirty–three younger adults (aged 18 to 33 years old) and thirty–one older adults (aged 62 to 87 years old) were recruited. Two–way repeated measures ANOVA analysis showed that: 1. The performance of the younger group for spatial orientation ability was significantly worse in the high visual perceptual stress condition (F(1,60) = 5.02, p < 0.05), while no significantly difference was found than that of the older group in medium stress condition (F(1,60) = 0.01, p > 0.05), in low stress condition (F(1,60) = 0.41, p > 0.05) and in no–noise condition (F(1,60) = 0.25, p > 0.05). 2. The older group’s performance of numerical ability was significant lower than that of the younger group in medium stress condition (F(1,55) = 20.28, p < 0.001), in low stress condition (F(1,55) = 13.58, p < 0.01) and in no-noise condition (F(1,55) = 210.95, p < 0.001), except in the high stress condition (F(1,55) = 0.99,p > 0.05). The age differences reduced gradually when the visual perceptual stress increased. 3. Significant age differences were found in inductive reasoning ability when the visual perceptual stress was matched between younger and older adults. The younger performed better in the four levels of visual perceptual stress than the older in medium stress condition (F(1,46) = 36.40, p < 0.001), in low stress condition (F(1,46) = 53.23, p < 0.001) and in no–noise condition (F(1,46) = 28.05, p < 0.001), while no difference was observed in the high stress condition (F(1,46) = 3.61, p = 0.064). The age differences also decreased gradually when the visual perceptual stress increased. The results supported the information–degradation hypothesis to some degree. The decline of visual function plays an important role in the aging of numerical ability and inductive reasoning ability. The relationship between visual perception and the aging of spatial orientation ability needs to be considered deeply. In conclusion, visual function may play an important role in the aging of PMA, while the role of visual function in the aging of PMA may be moderated by cognitive resource.

Key words: visual perceptual stress, primary mental ability, aging, the information–degradation hypothesis