Supplementary Table: Diagnostic, IQ, and matching details of studies included in the meta-analysis.
Study / DSM used / inclusion criteria / ASD Subgroups / IQ / Matching criteria*Ambery et al. 2006 / ICD10, minority had ADI (12) or ADOS (4) / Aspergers only / Short form WAIS-R: ASD VIQ 106.1 sd=15.7, range 82-135, PIQ 103.7 sd=19.2, range 75-147; Control VIQ 107.05, sd=13.1, range 93-140, PIQ 109.4, sd=18.5, range 80-140 / CA, sex, VIQ, PIQ, yrs education
Bennetto et al. 1996 / DSM3R, FSIQ>69, CARS / 11 autistic disorder,
8 PDDNOS / WISC-R five subtest pro-rated: ASD FSIQ 88.89 sd=11.1, VIQ 82.32 sd=15.2, PIQ 98.11 sd=15.9; Control FSIQ 91.74 sd=12.1, VIQ 88.26 sd=11.4, PIQ 97.58 sd=14.3 / not explicitly matched but did not differ on handedness, SES, PIQ, FSIQ; comparison group is clinical non-ASD
Ciesielski &Harris 1997 / DSM3 / all met "infantile autism" criteria / WISC-R or WAIS-R: ASD FSIQ 86, VIQ 86, PIQ 87; Control: VIQ 114, PIQ 113 / CA, SES; no attempts to match on IQ, inclusion criteria are PIQ>=70 for ASD and within one sd of the mean for controls
Geurts et al. 2004 / ADI-R, IQs>80 / none / WISC-R 4 subtests: ASD 98.3, sd=18.4, Control 111.5, sd=18) / CA
Goldstein et al. 2001 / ADI, ADOS, clinical interview to exclude Aspergers on basis of early language delay / HFA, excl. Aspergers, IQ>70 / WAIS-R: Autism FSIQ 97.57 sd=14.73, VIQ 99.60 sd=17.03, PIQ 95.65 sd=12.82; Control FSIQ 99.12 sd=10.29, VIQ 99.94 sd=10.8, PIQ 98.60 sd=10.14 / CA, gender, education, IQ
Griebling et al. 2010 / ADI, ADOS, clinical interview to exclude Aspergers on basis of early language delay, IQ>80 / HFA, excl. Aspergers / WAIS-R or WISC-R (scores not reported - refer to Hardan et al 2003 for details, but sample sizes of the two studies don't quite match: judging by range, excluded 2 with IQs slightly below 80; unclear which control was excluded) / not reported - all participants had IQs>80
Kaland et al.2008 / ICD-10, ADI-R, ADOS / all labeled Aspergers / WISC3: ASD FSIQ 109 sd=11.52, VIQ 108.92 sd=14.55, PIQ 107 sd=8.8; Controls FSIQ 109.62 sd=10.36, VIQ 100.15 sd=12.25, PIQ 106.92 sd=12.87 / IQ (one-to-one)
Kilinçasian et al. 2010 / DSM4, no speech delay, no MR (IQ>80), no chronic medical illness, no substance abuse, no sensory-motor disability / none / WISC-R: ASD FSIQ 105.52 sd=14.75, range 86-136; VIQ 111.17 sd=14.05, range 92-134; PIQ 98.35 sd=15.21, range 78-133; Control FSIQ 107.27 sd=13.39, range 82-138; VIQ 106sd=13.10, range 83-144; PIQ 107.44sd=13.57, range 82-131 / CA, gender, education, IQ
Liss et al. 2001 / Screened with Wing Autistic Disorder Interview Checklist, DSM3R, NVIQ>80 / none / Stanford Binet (1986) or Bailey Scale:ASD FSIQ 92.8 sd=13.5, NVIQ 101.3 sd=13.4, VIQ 87 sd=19.4;DLD FSIQ 97.5 sd=15.9, NVIQ 101.1, sd=16.2, VIQ 97.2 sd=12.8 / matched on NVIQ –control group is "clinical" (developmental language disorder) but selection criteria for this study was NVIQs > 80; DLD still 10pts higher on VIQ (97 v 87, p=.038)
Lopez et al. 2005 / ADI, ADOS, Gilliam Autism Rating Scale / none / WAIS3, PIQ>70 but not reported / not reported
Minshew et al. 1992 / DSM3R, FSIQ >70 and VIQ >70 / none / WAIS-R: ASD FSIQ 95.73 sd=13.61, VIQ 98.53 sd=21.63, PIQ 92.87 sd=10.72; Control FSIQ 96.47 sd=12.33, VIQ 99.07 sd=14.21, PIQ=93.27 / CA, FSIQ, gender, race (pairwise, IQ could not differ more than 5 points)
Minshew et al. 2002 / ADI, ADOS, excl. Aspergers on the basis of early language delay / HFA, excl. Aspergers / WAIS-R: ASD FSIQ 97.95 sd=16.01, VIQ 100.11 sd=17.99, PIQ 95.51 sd=14.69; Control FSIQ 100.90 sd=13.40, VIQ 101.5 sd=13.48, PIQ 99.95 sd=12.7) / CA, IQ, SES, gender
Nyden et al. 1999 / DSM4 and Gillberg Asperger criteria, IQ>70 / none / WISC3: ASD FSIQ 100.7 sd=16.3, PIQ 91.6 sd=13.8 / CA matched (no IQ for control group)
Ozonoff & Jensen,1999 / ADI, ADOS, DSM4, IQ>69 / none / WISC3: ASD FSIQ 95.2 sd=18.8, VIQ 93.3 sd=20, PIQ 98.6 sd=19.8; Control FSIQ 107.8 sd=10.8, VIQ 107.8 sd=12.3, PIQ 106.8 sd=12.5 / CA matched, FSIQ used as covariate as sig diff
Ozonoff & McEvoy, 1994 / DSM3R, CARS / 9 autistic disorder, 8 PDDNOS / WISC: ASD FSIQ 89.1 sd=11.8, VIQ 83.0 sd=16, PIQ 97.6 sd=16.7; Control FSIQ 95.6 sd=16.5, VIQ 91.8 sd=15.7, PIQ 100.6 sd=16.9 / IQ, SES, gender, CA
Ozonoff, Pennington, Rogers 1991 / DSM3R, no MR (FSIQ>69), CARS / 17 autistic disorder,
6 PDDNOS / WISC-R five subtest pro-rated: ASD FSIQ 89.52 sd=15.17, range 70-128, VIQ 82.91 sd=18.08, range 55-122, PIQ 98.35=sd 18.13, range 68-140; Control FSIQ 91.3 sd=18.75 range 55-134, VIQ 87.6 sd=17.79, range 55-122, PIQ 97.0 sd=18.38, range 63-140 / clinical control group matched pairwise on CA and sex and prorated VIQ
Pascualvaca et al. 1998 / DSM3R Autistic Disorder, CARS / none / WISC-3: ASD FSIQ 77.6 sd=14.5, range 55-107, VIQ 74.4 sd=16.4, PIQ 84.7 sd=17.9 / two control groups: (1)VMA and (2) PMA (1-to-1 within 6 months)
Ozonoff, 1995 / DSM4 / none / WISC3: Study2 ASD FSIQ=98.1 sd=18.2, VIQ=95.8 sd=18.9, PIQ=101 sd=19.3; Control FSIQ=99.1 sd=15, VIQ=100 sd=16.6, PIQ=98.3 sd=14; Study3ASD FSIQ=97.4 sd=17, VIQ=97.8 sd=17.4, PIQ=97.3 sd=18.9; Control FSIQ=101.9 sd=14.8, VIQ=102.2 sd=15.8, PIQ=101.5 sd=15.9 / CA, IQ; all participants FSIQ>70
Robinson et al. 2009 / DSM4, SCQ / none / WASI two-subtest version (matrix reasoning and vocab): ASD 103.53 sd=10.54; Control 104.8 sd=9.07
BPVS: ASD 99.7 sd=18.8; Control 100.94 sd=17.51 / CA, FSIQ, BPVS
Rumsey, 1985 / DSM3R, IQ>80 / clear history of "infantile autism" / WAIS: ASD FSIQ 104 sd=12, VIQ 103 sd=10, PIQ 104 sd=14; ControlFSIQ 113 sd=6, VIQ 113 sd=4, PIQ 111 sd=10 / matched on education; restrictive IQ inclusion also kept IQs close (limited to 90-119; only one participant with autism was tested in 80s) nevertheless the control group was 10 points higher on verbal (average, sig) and marginally sig on FSIQ with a 9pt diff.
Rumsey & Hamburger, 1988 / DSM3, WAIS<80 excluded (4 personally diagnosed by Leo Kanner!) / all met "infantile autism" criteria / WAIS: ASD VIQ 103.4 sd=9.47, PIQ 103.90 sd=13.63; Controls VIQ 112.8 sd=3.97, PIQ 111.10 sd=10.4 / education, IQ, sex, age, handedness; controls had to have IQ>90
Rumsey & Hamburger, 1990 / DSM3, IQ>80 / all met "infantile autism" criteria / WAIS: ASD FSIQ 95.7 sd=10.99, VIQ 96.4 sd=9.47, PIQ 95.9 sd=13.63; Control FSIQ 107.2 sd=7.57, VIQ 108.4 sd=7.89, PIQ 104.6 sd=10.54; Dyslexia MA control FSIQ 103.87 sd=9.72, VIQ 99.53 sd=9.52, PIQ 109.47 sd=11.82 / two matching groups: (1) CA normal, (2) Dyslexia MA. ASD differed from CA normal group on FSIQ and VIQ, matched dyslexia group on FSIQ and VIQ, but not PIQ; all groups match on CA
Schneider & Asarnow, 1987 / DSM3, IQ>70 / infantile autism / WISC-R: ASD FSIQ 85.73 sd=14.56, VIQ 80.13, sd=19.77, PIQ 93.67, sd=13.55; no control IQs / CA
Shu et al. 2001 / DSM3R; MR, fragile X, epilepsy, birth injury or head injury excl. / none / WISC:ASD 80, sd=12, range 65-112, IQ data only obtained for 15/26 ASD and none of the Controls / CA
Steel et al., 1984 / DSM3 / infantile autism / WAIS: FSIQ 90 VIQ 94 PIQ 89, Leiter IQ 80 / case-study
Sumiyoshi et al. 2011 / DSM4, also report CARS and AQ scores / 8 autistic disorder, 12 Asperger,
2 PDDNOS / WISC3 or WAIS-R: ASD 94.1 sd=17.8; Control 99.7 sd=8.6; Full version given to ASD but abbreviated given to non-ASD participants / none reported, tests not even run on IQ but superficially appear to "match"
Szatmari et al. 1990 / DSM3 for Autism, Wing adapted criteria for Asperger / 26 Asperger,
17 Autism / WISC-R or WAIS-R: Asperger 86.6 Autism 82.2 Control 101.5 / No matching; Control group is outpatient clinical with social impairment, not ASD
Tsuchiya et al. 2005 / DSM4 / none / WISC: ASD FSIQ 92.3 sd=12.5, VIQ 90.8 sd=17.8, PIQ 96.7 sd=12.1 / Control IQs not reported (perhaps not measured), CA matched
Voelbel et al. 2006 / DSM4, ADI (analyses run with and without those who don't meet cut-offs on ADI) / 11 HFA,
27 Asperger / WISC3: ASD FSIQ 99.37 sd=16.08, range 73-127, VIQ 104.55 sd=18.04, PIQ 94.42, sd=16.85; Control FSIQ 115.15, sd=9.41, range 93-133, VIQ 118.77, sd=12.34, PIQ 108.54, sd=9.54 / CA, SES
Winsler et al. 2007 / DSM4, IQ>84 / 9 HFA,
20 Asperger,
4 PDDNOS / not reported / CA
Yang et al. 2009 / DSM4 / 5 Asperger,
11 autism,
2 PDDNOS / Gong Non-Verbal Intelligence Test (Chinese):ASD(one child couldn't complete IQ test)NVIQ 96.68 sd=24.63, range 47-147; ControlNVIQ 118.23 sd=12.06, range 97-143 / CA matched, NVIQ used as covariate as groups differed.
*unless otherwise specified, comparison group are typically developing children (screening procedures for typically developing control groups were not often described in detail)