Low speed, or retardation of motor, perceptual and cognitive functioning has been considered to be an important aspect of depressive illness, particularly in the form described as psychotic depression (10,11,22,24,26,29,30,32). However negative findings have also been reported. Thus, Hall and Stride (17) failed to find a difference in reaction times between depressive and normal controls. Friedman (12) found only a minimal effect of severe depression on cognitive functioning. Both Hall and Stride and also Friedman stressed the importance of matching the subjects for age and education, which had not been done in many previous studies. Age is a particularly important variable in relation to the speed of perception and more complex information processing (1,8,16,27). Friedman matched his depressed and nondepressed subjects carefully for age and education and administered to them a large battery of cognitive, perceptual and psychomotor tests. He found that although depressed patients subjectively assessed their performance as being very poor they were significantly impaired on only nine test scores out of eighty-two and only on three scores at the .01 level of significance. However he did not attempt to separate speed tests from power (level) tests. There is ample evidence that the power (level) factors of cognitive functioning are relatively independent of the speed factors (4,14,18,19,24,25,26). The perusal of Friedman's results suggests that most of the tests on which
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