Table 1.

Characteristics of research participants

	Age Group			Age R2
	18–39	40–59	60–93	Age	Age2	Age3
N	89	132	105
Age	28.3 (6.0)	49.8 (5.4)	70.9 (7.7)
Prop. Females	.66	.66	.60	.00	.01	.01
Years of education	15.2 (2.2)	15.8 (2.8)	15.9 (2.7)	.02	.02*	.00
Health	1.9 (0.8)	2.1 (0.9)	2.3 (1.0)	.04*	.00	.00
MMSE	29.2 (1.2)	28.9 (1.3)	28.6 (1.8)	.03*	.00	.03*
Scaled scores
Vocabulary	12.8 (3.1)	12.2 (3.0)	13.6 (2.9)	.01	.03*	.04*
Digit symbol	11.0 (2.8)	10.7 (2.8)	11.4 (2.7)	.01	.00	.01
Cognitive ability scores
Fluid ability (gF)	.45 (.81)	.03 (.73)	−.39 (.71)	.22*	.00	.03*
Episodic memory	.36 (.75)	.02 (.74)	−.31 (.85)	.15*	.01	.04*
Perceptual speed	.65 (.71)	.09 (.70)	−.65 (.79)	.37*	.02*	.00
Vocabulary	−.33 (.83)	.02 (.90)	.27 (.83)	.06*	.01	.04*

Note: Values in parentheses are standard deviations. Health was a rating on a scale from 1 for Excellent to 5 for Poor. MMSE was the score on the mini mental status examination (Folstein et al., 1975) often used as a preliminary screening instrument for dementia. The cognitive ability scores were the average z-scores of six reasoning and spatial visualization measures (Raven’s progressive matrices, Shipley abstraction, letter sets, spatial relations, paper folding, form boards) for fluid ability, three episodic memory measures (logical memory, word recall, paired associates), three perceptual speed measures (digit symbol substitution, letter comparison, pattern comparison), and four vocabulary measures (WAIS III vocabulary, Woodcock–Johnson picture vocabulary, synonym vocabulary, antonym vocabulary). See Salthouse et al., 2006 for further details of the reference cognitive tasks.

^*p < .01.