A factorial approach in aging research

The population of developed countries is aging at an ever increasing rate. Even in the absence of neurodegenerative diseases, aging affects perceptual and cognitive functions that are crucial for everyday life. The effects of healthy aging on cognitive abilities are well studied, and it has been suggested that there is a common cause for cognitive decline. However, age does not only affect cognitive but also perceptual abilities. Surprisingly, our data disprove the existence of common factors underlying perceptual change with age. For the first time, we employed a battery of nine tests that measure visual discrimination and ten tests that measure subjective perception, such as illusion strength. Generally, older adults performed worse than younger adults, whereas subjective tests did not differ strongly. Surprisingly, we found very low correlations between all tests, so that for example performance in one test was unrelated to performance in other tests (i.e., performance in coherent motion was not correlated to performance in biological motion). Our results show that anti-ageing perceptual programs need to be strongly tailored to the individual needs of people. Moreover, our results show the importance of measuring individual differences and question the use of average results, especially in aging research.