Table 2.

Cognitive performance of the PKU group (English and Italian PKU participants; N = 56). Z scores calculated from respective control groups (N = 30 and N = 19). To facilitate interpretation, for all scores, higher Z-score reflect worse performance. Scores in bold are significantly higher than expected. ms. = milliseconds; sec. = seconds

	PKU Overall Z score
	Mean	SD	Diff from controls (t-test)
IQ	0.8	1.3	p < .001
Visual attention RTs
Simple Detection - ms.	0.3	1	n.s.
Detention with Distractors – ms.	0.8	1.6	p < .01
Feature Search – ms.	1.5	2.3	p < .001
Conjunction Search m.	1.2	1.7	p < .001
Visual attention accuracy
Detention with Distractors - % errors	0.2	1	n.s.
Feature Search - % errors	0.2	2.6	n.s
Conjunction Search - % errors	−0.1	0.8	n.s
Visuo-motor coordination
Pegboard (sec.)	0.9	1.9	p < .01
Digit Symbol (%errors in 90 s.)	0.7	1.2	p < .01
Trail-Making Test A: (sec.)	0.8	1.9	p < .01
Executive functions
WCST
Total errors	0.4	1.6	n.s.
Perseverative responses	0.1	1.1	n.s.
N of Completed Categories	0.5	1.9	p = .06
Trail-Making Tests
B (sec.)	0.6	1.5	p = .01
B-A (sec.)	0.5	1.7	p = .06
Verbal Fluency
Letter (correct answers)	0.6	1	p < .01
Semantic (correct answers)	0.8	1.3	p < .001
Short term memory
Digit span	0.3	1.1	n.s.
Corsi Block span	0.0	1.1	n.s.
Sustained attention
RVP (% of errors)	0.7	1.3	p < .01
Learning
Rey Auditory Verbal Learning Test
Trial A1-A5 (% errors)	0.2	1.2	n.s.
Retention (% errors A6)	0.3	1.4	n.s.
Delayed Recall (% errors)	0.3	1.3	n.s.
Paired Associate Visual learning
(% errors)	0.7	1.9	p = .02
Overall (excluding IQ)
Mean	0.5	0.8	p < .001