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Table 3 Twin sample characteristics for the behavioral variables

From: Sex differences in brain structure: a twin study on restricted and repetitive behaviors in twin pairs with and without autism

 All (N = 150)Males (N = 88)Females (N = 62)χ2, P
A) Mean scores
IQ mean (SD)97.86 (15.65)97.22 (14.42)98.77 (17.31).14, .708
Range62–14262–12363–142 
ADI-R RRBI mean (SD)1.02 (1.62)1.10 (1.81)0.90 (1.33).08, .774
Range0–100–100–5 
ADI-R social interaction mean (SD)4.08 (5.13)4 (5.41)4.19 (4.76).27, 0.601
Range0–250–250–16 
Pairs ADI-R RRBI differencea372116 
 ASD Discordant pairs18   
 ASD Concordant pairs8   
 No-ASD pairs15   
SRS-2 total score mean (SD)41.66 (30.97)40.65 (29.50)43.10 (33.15).01, .927
Range0–1314–1310–130 
SRS-2 RRB mean (SD)5.85(6.25)6.08 (6.41)5.52 (6.07).27, .601
Range0–260–260–23 
SRS-2 social cognition mean (SD)7.66 (6.50)7.20 (5.88)8.31 (7.29).29, .591
Range0–290–230–29 
ADOS-severity2.66 (2.25)
1–10
2.91 (2.44)
1–10
2.31 (1.92)
1–8
3.07, 0.080a
ADOS-severity in ASD-diagnosed Participants (20 males, 12 females)5.78 (2.52)
1–10
6.40 (2.44)
1–10
4.75 (2.42)
2–8
3.43, 0.064a
Handedness (mean)66.0766.7265.151.65, .199
B) Within-pair differences
IQ mean (SD)10.15 (8.81)9.84 (9.48)10.58 (7.90).78, .377
Range0–390–390–31 
ADI-R RRBI mean (SD)1.05 (1.36)1.022 (1.36)1.097 (1.40).07, .790
Range0–50–50–5 
ADI-R social interaction mean (SD)2.93(4.27)3.23 (5.27)2.52 (3.85).02, .890
Range0–250–250–15 
SRS-2 total score mean (SD)23.05 (26.22)23.39 (25.55)22.58 (27.57)< .001, .991
Range0–1010–960–101 
SRS-2 RRB mean (SD)4.92 (5.77)5.07 (5.93)4.71 (5.62).05, .827
Range0–220–220–22 
SRS-2 SCOG mean (SD)5.4(5.35)5.32(4.79)5.52(6.14).14, .709
Range0–220–190–22 
  1. SD standard deviation, IQ overall intellectual quotient measured with WISC/WAIS. Handedness: assessed with Edinburgh handedness inventory, a scale from  100/+ 100, where  100 represents totally left handed, and +100 totally right handed. P-values and chi-squares are given from χ2 tests comparing males with females
  2. aADI-R C difference refers to the number of pairs that have a within-pair difference on the ADIR C score of > 0 and therefore contribute most to the within-pair analyses
  3. **= p <0.01, * p<0.05, . = p< 0.1