It has recently been suggested thot Ihrge Foportion of the age-related influences on ,nan! meanr.res of cognitive functioning h mediated through a singk common Jactor. Thi hypothesis -h^ brrn suppoied by the disioviry that much of the age'relared variance in diflerent cognitive measures is shared, and is not iiitinct or-independent. Thr1yearlier results were replicated in this proiect, and il was also discovered that measures of corrected visual acuity ai processing speed share avery-large proportion of the age-relatedvariance in mcasures of working memory, ̂ roiiotin1" learning' and concept identification. The apparent imptication is that the commonfacir that af,pears n iontribute to age'related dffirences in ma-ny.cognitive measures is quite broad and may refuit a relativefy'general reduction in central nemous system functioning.