| Abstract: | Two analytical methods are proposed to evaluate the extent to which the age-related influences in a set of variables are independent of one another. Application of the methods to 16 different data sets, representing a total of 169 variables and 4505 subjects, reveals that as few as one or two distinct factors may be sufficient to account for a large proportion of the age-related variance in a variety of cognitive variables. These results therefore imply that a relatively small number of independent "causes" may be responsible for a substantial percentage of the age-related declines apparent in many measures of cognitive functioning. |
