Table 2.

Task Parameters, Performance, and Reliability on 5 Versions of the DPX

Version	Trial-Type	Number of Trials (%)	Schizophrenia Patients		Controls
			% Errors (SD)	α	% Errors (SD)	α
Long forms (ISI 4000 ms)
Form 1	AX	88 (68.75)	9.1 (8.1)	.87	3.7 (4.2)	.78
	AY	16 (12.5)	20.1 (17.0)	.71	10.3 (10.2)	.47
	BX	16 (12.5)	19.9 (21.2)	.83	8.3 (12.5)	.74
	BY	8 (6.25)	4.2 (8.5)	.32	0.9 (3.7)	.15
Form 2	AX	80 (62.5)	10.2 (10.2)	.90	4.3 (5.1)	.80
	AY	24 (18.75)	14.1 (14.6)	.80	7.7 (9.2)	.68
	BX	16 (12.5)	17.3 (19.7)	.82	9.5 (13.8)	.76
	BY	8 (6.25)	5.9 (9.6)	.27	2.1 (6.5)	.43
Form 3	AX	76 (59.38)	10.5 (10.1)	.90	5.2 (6.9)	.88
	AY	24 (18.75)	14.3 (14.2)	.78	6.6 (8.1)	.64
	BX	20 (15.63)	20.5 (22.0)	.85	9.0 (12.9)	.80
	BY	8 (6.25)	5.4 (10.3)	.43	1.8 (5.0)	.14
Short forms (ISI 2000 ms)
Form 1	AX	88 (68.75)	9.1 (9.2)	.90	2.8 (3.9)	.80
	AY	16 (12.5)	18.1 (15.1)	.65	9.8 (5.0)	.39
	BX	16 (12.5)	20.4 (20.4)	.79	7.8 (4.8)	.53
	BY	8 (6.25)	7.1 (11.1)	.28	1.8 (7.4)	.21
Form 2	AX	80 (62.5)	9.6 (9.9)	.90	3.2 (12.3)	.84
	AY	24 (18.75)	14.2 (13.1)	.74	6.2 (6.4)	.58
	BX	16 (12.5)	20.2 (19.8)	.80	8.2 (5.0)	.73
	BY	8 (6.25)	7.1 (10.3)	.27	2.1 (4.8)	.38

Note: ISI, interstimulus interval (time between the offset of the cue and the onset of the probe, in milliseconds); Reliability is measured by Cronbach’s α for available participants; For all versions of the task, the number of trials was 128, cue length was 1000 ms, probe length was 500 ms, and intertrial interval was 1200 ms. Long form 1 represented the standard version of the task. The other task versions were developed by altering the standard version’s ISI and critical trial (AY or BX) frequencies. Long forms 2 and 3 were created by increasing the frequency of one (long form 2; AY trials) or both (long form 3; AY and BX trials) critical trials. Short form 1 was created by reducing the ISI, whereas short form 2 reduced ISI and increased AY trial frequency. AY or BX trial frequency increases were accommodated by a reduction in AX trial frequency (ie, the expectancy manipulation).