Table 1. Demographics, clinical measures, and task performancea.

	SZ (n=22)	HC (n=19)	t/X 2	P-value
Gender (% male)	77.3	57.9	1.77	0.31
Age	39.41 (6.70)	36.47 (12.12)	−0.74	0.47
Parental occupationb	6.70 (5.05)	7.50 (4.76)	12.52	0.25
Smoking status (% smokers)	72.7	42.1	4.82	0.03
Smoking (packs per day)	0.66 (0.60)	0.36 (0.50)	−1.74	0.09
Diagnosis
Schizophrenia	15
Schizoaffective disorder	7
Illness duration (in years)	17.68 (11.53)
Antipsychotic medication
First generation	2
Second generation	17
First and second generations	1
Clozapinec	2
BPRS d
Total	30.27 (8.86)
Positive	5.77 (3.74)
Negative	4.27 (1.75)
RBANS total index	76.14 (9.33)	93.32 (11.49)	5.28	<0.01
Prediction error task
Total reward earned ($)	11.71 (1.59)	12.41 (1.14)	1.59	0.12
Mean prediction error ($)	−0.19 (0.33)	−0.31 (0.33)	−1.13	0.26
Task performancee	0.03 (0.01)	0.01 (0.02)	2.32f	0.13

Abbreviations: HC, healthy controls; RBANS, Repeatable Battery for the Assessment of Neuropsychological Status; SZ, schizophrenia.

^aMean (s.d.) unless indicated otherwise.

^bRanks determined from Diagnostic Interview for Genetic Studies (1–18 scale); higher rank (lower numerical value) corresponds to higher socioeconomic status. Parental occupation unknown in three HC and two patients with schizophrenia, n=36.

^cOne SZ with clozapine monotherapy and one SZ with combination of clozapine and ziprasidone.

^dBrief Psychiatric Rating Scale (1–7 scale); positive (conceptual disorganization, hallucinatory behavior, and unusual thought content); negative (emotional withdrawal, motor retardation, and blunted affect).

^eTo assess diagnostic status as predictor of trial response, linear regression was conducted (button press as dependent variable, sessions and trials as fixed independent factors, and group as random factor). Values reported in parentheses are s.e.

^fReported value is F-statistic.