Intellectual de-differentiation and deficit with age--artifacts?
D000368:Aged; D000375:Aging; D004522:Educational Status; D005163:Factor Analysis, Statistical; D005260:Female; D005860:Germany, West; D006262:Health; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D009790:Occupations; D012107:Research Design; D012737:Sex Factors; D012923:Social Class