65 Executive functioning in ASD

yields a purer measure of that particular EF ability. Secondly, we looked for JVU]LYNPUN L]PKLUJL *VU]LYNLUJL PZ VI[HPULK ^OLU KPɈLYLU[ PUZ[Y\TLU[Z HZZLZZPUN [OL ZHTL ,- `PLSK [OL ZHTL ÄUKPUNZ :LSLJ[PUN OPNOS` KPɈLYPUN instruments that claim to assess the same underlying EF ability increases [OLWYVIHIPSP[`[OH[JVU]LYNLU[KLÄJP[ZHYLK\L[VHUHJ[\HS,-PTWHPYTLU[ HUKUV[TLYLS`[VHKLÄJPLUJ`PUHU`VM[OLHKKP[PVUHSUVU,-WYVJLZZLZ>L therefore measured each EF domain with several instruments tapping into KPɈLYLU[HKKP[PVUHSWYVJLZZLZ;OPYKS`^OLUHWHY[PJ\SHY,-KLÄJP[^HZMV\UK we sought to dissociate it from any confounding variables. Accordingly, we included several non-EF measures that are involved in the EF tasks. Finally, PMNYV\WKPɈLYLUJLZ^LYLHSZVMV\UKVUWVZZPISLJVUMV\UKZ^LPU]LZ[PNH[LK whether EF impairments remained while controlling for these confounds. Confounding variables comprised various non-EF or EF abilities. For example, Miyake and Friedman (2012) suggested that inhibition is a common JVTWVULU[PUHSS,-[HZRZZVMVYLHJOVIZLY]LK,-PTWHPYTLU[^L]LYPÄLK whether it remained after controlling for inhibition impairments.

(UV[OLY O`WV[OLZPZ HKKYLZZPUN [OL PUJVUZPZ[LU[ ÄUKPUNZ PU [OL ,- ASD literature postulates that individuals with ASD are more impaired in open-ended compared to highly structured assessment situations (Gioia, Isquith, Kenworthy, & Barton, 2002; White, 2013; White, Burgess, & Hill, 2009). In open-ended (or so-called ‘self-ordered’) tasks, there are several possible strategies to perform the task and the participant has to implicitly infer the correct behaviour while being free in strategy choice. These tasks are considered to be more ecologically valid compared to highly structured tasks. In highly structured or constrained EF tasks, explicit instructions clearly indicate what the participant has to do and how this has to be done. This hypothesis emerged from the striking observation that individuals with ASD VM[LUKPZWSH`WYVUV\UJLK,-KLÄJP[ZPUKHPS`SPML^OPSLWLYMVYTPUNHKLX\H[LS` on highly structured laboratory tasks (Kenworthy et al., 2008). White and colleagues (2009) compared the performance of children with ASD versus Typically Developing (TD) children on a series of constrained versus open- ended tasks and showed that all open-ended tasks revealed impairments in ASD, while none of the more constrained tasks did. In line with this hypothesis, we included both an open-ended and a more constrained task ]HYPHU[MVY[OLJVNUP[P]LÅL_PIPSP[`NLULYH[P]P[`HUK^VYRPUNTLTVY`KVTHPUZ (Note that inhibition is hard to measure ‘purely’ with an open-ended task, while measuring planning seems to be incompatible with a highly structured task). Furthermore, task administration was complemented with parent reports of EF in daily life, which may be considered as the most open-ended assessment situation.

)LZPKLZ KPɈLYLUJLZ PU [HZR JOHYHJ[LYPZ[PJZ PUJVUZPZ[LU[ ÄUKPUNZ HTVUN ,- Z[\KPLZ TPNO[ IL K\L [V KPɈLYLUJLZ PU ZHTWSL JOHYHJ[LYPZ[PJZ 0KLU[PM`PUN[OLWHY[PJ\SHY,-WYVÄSLVMPUKP]PK\HSZ^P[O(:+YLX\PYLZJVTWHYPUN their performance with that of an appropriate control group without ASD. (WHY[ MYVT KPɈLYLUJLZ PU JSPUPJHS Z[H[\Z WHY[PJPWHU[ NYV\WZ JV\SK KPɈLY VU THU` V[OLY HZWLJ[Z [OH[ TH` PUÅ\LUJL [OLPY ,- HIPSP[PLZ 08 MVY PUZ[HUJL

66 Executive functioning in ASD

OHZILLUZOV^U[VJVYYLSH[L^P[OZVTLI\[UV[HSS,-TLHZ\YLZ(YɈH" Friedman et al., 2006). Age as well has been associated with EF performance. +PɈLYLU[ TH[\YH[PVU [YHQLJ[VYPLZ OH]L ILLU KLZJYPILK MVY KPɈLYLU[ ,- measures depending on task complexity, with maturation being reached later for the more complex tasks (for reviews see, Best & Miller, 2010; Best, Miller, & Jones, 2009). Given these associations, it is important to control MVYNYV\WKPɈLYLUJLZPUHNLHUK08/V^L]LY[OL^H`PU^OPJO[OPZJVU[YVS PZHJJVTWSPZOLKTH`PUK\JLKPɈLYLUJLZPUJVNUP[P]LWYVÄSLZHUKTH`[O\Z contribute to the observed inconsistencies between studies (Mottron, 2004; Shaked & Yirmiya, 2004).

4VYLV]LY KPɈLYLUJLZ IL[^LLU Z[\KPLZ PU HNL 08 HUK NLUKLY VM WHY[PJPWHU[ZTH`HSZVYLZ\S[PUHKPɈLYLU[WH[[LYUVMPTWHPYLKHUKPU[HJ[,- abilities in ASD. Thus far, few studies have directly investigated this topic. In WHY[PJ\SHY[OLLɈLJ[VMNLUKLYVU,-HIPSP[PLZPU(:+OHZIHYLS`ILLUL_WSVYLK MVY H NLULYHS YL]PL^ VM NLUKLY LɈLJ[Z PU (:+ ZLL 2PYRV]ZRP ,U[PJV[[ & Fitzgerald, 2013). Since ASD is far more common in boys than in girls, many studies only include boys or ensure that the gender ratio is group-wise matched.

In the present study, we investigated EF in children (8-11 years) versus adolescents (12-18 years) and in boys versus girls with ASD as compared to TD controls, group-wise matched for age, gender, performance IQ (PIQ) and M\SSZJHSL08-:083HYNLZHTWSLZ^LYLYLJY\P[LK[V`PLSKZ\ɉJPLU[Z[H[PZ[PJHS WV^LY[VKL[LJ[HU`YLSPHISLNYV\WKPɈLYLUJLZ

0U HKKP[PVU [V L_HTPUPUN NYV\W KPɈLYLUJLZ PU ,- HUK WV[LU[PHS associations with age, gender and IQ, we also aimed to address the relationship between EF and ASD symptoms. Executive dysfunctions have been particularly related to the restricted, repetitive behaviours and interests (RRBIs) of individuals with ASD (Happé & Ronald, 2008; Hill, 2004; Russell,   ,ZWLJPHSS` PTWHPYTLU[Z PU YLZWVUZL PUOPIP[PVU JVNUP[P]L ÅL_PIPSP[` and generativity have been proposed to provoke these RRBIs (Turner, 1997). Concerning the relationship between EF and social (interaction and JVTT\UPJH[PVU (:+ Z`TW[VTZ KPɈLYLU[ VWPUPVUZ L_PZ[ :L]LYHS H\[OVYZ OH]L Z\NNLZ[LK [OH[ KLÄJPLU[ ,- TH` HSZV JH\ZL ZVTL VM [OL ZVJPHS problems in ASD (Hill, 2004; Russell, 1997). More recently, however, Happé and Ronald (2008) suggested that no single cognitive account can explain [OL^OVSLHYYH`VM(:+Z`TW[VTZI\[[OH[KPɈLYLU[HJJV\U[ZPUKLWLUKLU[S` YLSH[L [V KPɈLYLU[ Z`TW[VT KVTHPUZ ^P[O L_LJ\[P]L K`ZM\UJ[PVUZ ILPUN ZLSLJ[P]LS`HUKZWLJPÄJHSS`HZZVJPH[LK^P[O99)0Z;VPU]LZ[PNH[L[OPZM\Y[OLY we examined the association between EF performance and both RRBIs and social problems.

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