Table 3.

Correlations Between Processing Speed and Executive Control Measures in Experiment 1

	Perceptual Speed .384	Working Memory^ .357	Inhibition .240
Psychomotor Speed .236	.310*	−.067	.382**
Perceptual Speed .384	-	−.472**	.494**

Note—Perceptual speed does not show adequate discriminant validity from executive control constructs. Working memory but not inhibition shows discriminant validity from psychomotor speed. Psychomotor and perceptual speed show an ambiguous discriminant validity pattern. Within-construct correlations are noted in column and row headings, and between-construct correlations are noted in table cells. When the between-construct correlation is smaller than the within-construct correlations, the constructs have good discriminant validity. n = 58;

^*p < .05;

^**p < . 01

^{^}negative because larger is better for WM. Psychomotor Speed composite = average of offset RT, simple RT, box completion, horizontal line marking, and digit copying z scores; Perceptual Speed composite = average of color naming, choice RT, color task, choice RT, color and shape tasks, choice RT, quantity and identity tasks, and addition and subtraction tasks z scores; Inhibition composite = average of stop signal reaction time, stop signal task, color minus non-color word completion time, Stroop task, and antisaccade percent errors, antisaccade task z scores; Working Memory composite = average of digit span backward, spatial span backward, reading span total items correct, counting span total item correct, and operation span total items correct z scores.