Grade 1

Grade 2

Grade 3

Grade 4

F

P

CPM

17.0

(5.1)

20.5

(5.8)

22.9

(4.9)

22.7

(5.9)

7.53

P < .0005

Stroop N

26.3

(8.0)

26.6

(10.1)

20.8

(5.7)

19.6

(4.9)

7.22

P < .0001

Stroop C

26.1

(7.2)

23.4

(9.3)

17.0

(3.5)

15.3

(7.6)

20.26

P < .0001

Stroop In

40.1

(14.3)

50.1

(21.1)

41.9

(10.1)

40.4

(11.8)

2.95

P < .05

Stroop E

13.8

(13.8)

23.5

(19.1)

21.1

(9.6)

20.9

(13.1)

2.57

P = .057

Trail A

156.6

(67.2)

120.6

(36.3)

108.2

(36.2)

114.2

(38.4)

6.50

P < .0001

Trail B

273.9

(83.2)

236.8

(82.9)

187.2

(54.2)

173.7

(46.8)

13.49

P < .0001

Digit F

3.9

(.7)

4.1

(.8)

4.3

(.9)

4.4

(.7)

2.65

P = .052

Digit B

2.3

(.5)

2.5

(.7)

2.6

(.6)

2.8

(.7)

4.16

P < .01

Digit S

6.1

(.8)

6.7

(1.2)

6.8

(1.2)

7.2

(1.1)

4.90

P < .005

Symbol S

12.8

(4.0)

16.5

(3.9)

17.3

(4.5)

17.5

(6.7)

6.60

.001

HDCT

9.9

(2.5)

9.6

(2.3)

10.3

(2.1)

10.7

(2.3)

1.27

n.s

Read A

16.9

(6.1)

22.3

(3.7)

21.7

(4.1)

21.9

(4.10)

8.70

P < .0001

Read F

6.9

(7.9)

18.6

(9.1)

29.3

(19.3)

26.3

(12.7)

15.94

P < .000