Consistency does not aid detection of feigned symptoms, overreporting does: Two explorative studies on symptom stability among truth tellers and feigners

Figures & data

Figure 1. Mean symptom reports for truth tellers (n = 32) and feigners (n = 32) across the 5-day period (Study 1). Error bars are 95% Confidence Intervals (CIs).

Table 1. Means and standard deviations of symptom intensity reports on all five days, with t-test results.

	Truth tellers		Feigners		t-test	p	Cohen’s d
N	32		32		df = 68
Days	M	(SD)	M	(SD)
Day 1	3.88	(2.30)	5.31	(2.55)	2.37	<.05	0.59
Day 2	2.63	(2.39)	5.63	(2.08)	5.36	<.001	1.34
Day 3	2.53	(2.44)	5.25	(2.27)	4.62	<.001	1.15
Day 4	2.44	(2.98)	5.25	(2.68)	3.97	<.001	0.99
Day 5	2.53	(2.38)	4.41	(2.71)	2.94	<.01	0.74

Table 2. SRSI subscales scores of Truth tellers and Feigners.

	Truth tellers		Feigners		F(1,62)	p	Cohen’s d
	32		32
N	M	(SD)	M	(SD)
Genuine symptom scales
Cognitive	2.13	(2.33)	2.47	(2.66)	0.30	.58	0.14
Depressive	1.84	(1.63)	3.09	(2.28)	6.38	<.02	0.64
Pain	0.97	(1.26)	3.41	(3.05)	17.51	<.01	1.06
Nonspecific somatic	3.56	(3.10)	5.06	(3.16)	3.67	.06	0.48
PTSD/anxiety	1.19	(1.80)	2.09	(2.51)	2.76	.10	0.42
Total	9.69	(7.77)	16.13	(11.3)	7.02	<.02	0.67
Pseudosymptom scales
Cognitive/memory	0.44	(0.72)	1.00	(1.16)	5.42	<.05	0.88
Motor	0.16	(0.45)	0.81	(1.06)	10.40	<.01	0.82
Neurological: sensory	0.44	(0.76)	1.16	(1.82)	4.27	<.05	0.52
Pain	0.22	(0.49)	0.81	(1.18)	6.95	<.02	0.67
Anxiety/depression	0.50	(0.84)	1.00	(1.48)	2.76	.10	0.42
Total	1.75	(1.81)	4.78	(4.56)	12.19	<.01	0.88
Cutoff points	Fail	Pass	Fail	Pass
>9 of pseudosymptoms	0%	100%	15%	85%
>6 of pseudosymptoms	0%	100%	31%	69%

Note. SRSI = Self-Report Symptom Inventory; PTSD = post-traumatic stress disorder. Area under the curve (AUC) = .685.

Figure 2. Mean symptom reports for truth tellers (n = 48) and feigners (n = 28) across the 5-day period (Study 2). Error bars are 95% CIs.

Table 3. Means and standard deviations of symptom intensity scores on all five days, including independent t-test results.

	Truth tellers		Feigners		t-test	p	Cohen’s d
N	42		28		df = 68
Days	M	(SD)	M	(SD)
Day 1	4.26	(2.51)	5.75	(2.08)	2.60	.012	.60
Day 2	3.16	(2.10)	4.89	(2.37)	3.19	.002	.62
Day 3	3.45	(2.36)	5.57	(2.48)	3.60	.001	.85
Day 4	3.45	(2.57)	5.17	(2.69)	2.70	.009	.69
Day 5	3.42	(2.70)	5.50	(2.71)	3.13	.003	.72

Table 4. Means of symptoms from SRSI subscales for both groups.

	Truth tellers		Feigning group		F(1, 68)	p	Cohen’s d
	42		28
N	M	(SD)	M	(SD)
Genuine symptom scales
Cognitive	2.30	(2.47)	3.68	(3.17)	4.09	.047	0.49
Depressive	2.50	(2.14)	3.07	(2.36)	1.18	.281	0.26
Pain	3.12	(1.89)	4.57	(3.30)	5.46	.022	0.56
Nonspecific somatic	5.02	(3.23)	6.68	(2.86)	4.81	.032	0.53
PTSD/anxiety	2.21	(2.16)	1.46	(1.77)	2.01	.161	0.34
Total	15.01	(8.82)	19.46	(9.40)	3.91	.052	0.48
Pseudosymptoms scales
Cognitive/memory	0.71	(1.13)	1.92	(2.26)	8.85	.004	0.72
Neurological: Motoric	0.36	(0.76)	0.82	(1.54)	2.81	.098	0.41
Neurological: Sensory	0.81	(1.31)	1.21	(1.64)	1.31	.257	0.28
Pain	0.67	(1.14)	1.32	(1.70)	3.73	.058	0.47
Anxiety/depression	1.00	(1.64)	1.25	(1.80)	0.36	.549	0.14
Total	3.55	(4.53)	6.54	(7.38)	4.41	.039	0.51
Cutoff points	Fail	Pass	Fail	Pass
>9 of pseudosymptoms	12%	88%	21%	79%
>6 of pseudosymptoms	19%	81%	28%	72%

Note. PTSD = post-traumatic stress disorder. Area under the curve (AUC) = .637. One-way analysis of variance (ANOVA) results are also displayed.

Figure 3. Mean symptom reports for truth tellers (n = 74) and feigners (n = 60) across the 5-day period (Study 1 & Study 2). Error bars are 95% CIs.

Table 5. Means of symptoms from SRSI subscales for both groups. One-way ANOVA results also displayed.

	Truth tellers		Feigning group		F(1, 132)	p	Cohen’s d
N	74		60
	M	(SD)	M	(SD)
Genuine symptom scales
Cognitive	2.23	(2.39)	3.03	(2.95)	3.030	.084	0.28
Depressive	2.20	(1.96)	3.08	(2.29)	5.720	.020	0.40
Pain	2.19	(1.95)	3.95	(3.19)	15.370	<.001	0.66
Nonspecific somatic	4.39	(3.23)	5.81	(3.10)	6.650	.011	0.46
PTSD/anxiety	1.74	(2.07)	1.80	(2.20)	0.023	.878	0.00
Total	12.75	(8.75)	17.68	(10.52)	8.750	.004	0.50
Pseudosymptoms scales
Cognitive/ memory	.60	(.97)	1.44	(1.80)	11.720	.001	0.59
Neurological: Motoric	.27	(.65)	.81	(1.29)	10.080	.002	0.55
Neurological: Sensory	.65	(1.11)	1.18	(1.72)	4.700	.032	0.35
Pain	.47	(.94)	1.05	(1.45)	7.690	.006	0.46
Anxiety/ depression	.78	(1.36)	1.11	(1.62)	1.660	.200	0.20
Total	2.77	(3.70)	5.60	(6.05)	11.070	.001	0.59
Cutoff points	Fail	Pass	Fail	Pass	AUC
>9 of pseudosymptoms	7%	93%	18%	82%	0.654
>6 of pseudosymptoms	11%	89%	30%	70%

Notes. SRSI = Self-Report Symptom Inventory; PTSD = post-traumatic stress disorder.