127 Local-global visual processing in ASD

LɈLJ[^P[O;+IV`ZKLTVUZ[YH[PUNHTVYLSVJHSS`VYPLU[LKWYVJLZZPUNZ[`SL [OHU ;+ NPYSZ ;OLZL ÄUKPUNZ HYL PU SPUL ^P[O YLWVY[Z VM )VV[O  ^OV showed that TD boys are more part-oriented than girls, although both genders have comparable local and global processing abilities. Booth (2006) only L_HTPULKNLUKLYLɈLJ[ZPU;+PUKP]PK\HSZ6US`HML^Z[\KPLZPU]LZ[PNH[LK NLUKLYLɈLJ[ZPUPUKP]PK\HSZ^P[O(:+HUK[OL``PLSKLKPUJVUZPZ[LU[ÄUKPUNZ WYVIHIS` K\L [V KPɈLYLUJLZ PU [HZR WHYHKPNT HUK WHY[PJPWHU[Z» HNL )€S[L Duketis, Poustka, & Holtman, 2011; Lai et al., 2012). We observed no gender LɈLJ[ZMVYPUKP]PK\HSZ^P[O(:+I\[MV\UK[OH[VUS`NPYSZ^P[O(:+OHKHTVYL locally oriented processing style compared to TD girls, at least for participants aged 8-18 years (see section 4.1.3, for a more elaborate discussion).

>LKPKVIZLY]LWYVUV\UJLKHNLLɈLJ[ZVUHSSTLHZ\YLZL_JLW[[OL Attention to Detail scale of the DFlex questionnaire. On all tasks measuring local and global processing abilities, adolescents outperformed children. Furthermore, adolescents adopted a more globally oriented processing Z[`SLVU[OL96*-[HZR;OLZHTLWH[[LYU^HZJVUÄYTLKI`[OLJVYYLSH[PVU analyses, showing a negative correlation between age and performance on all local-global processing tasks. This implies that, as individuals grow older, both their local and global processing abilities improve and they develop HTVYLNSVIHSS`VYPLU[LKWYVJLZZPUNZ[`SL;OLZLÄUKPUNZJVUÄYTWYL]PV\Z reports (Booth, 2006; Happé & Booth, 2008). Additionally, we observed a NYV\WI`HNLPU[LYHJ[PVUVU[OL*4[HZR^P[OZPNUPÄJHU[NYV\WKPɈLYLUJLZMVY children but not for adolescents (see above, for a more elaborate discussion). ;OPZYLZ\S[Z\NNLZ[Z[OH[PUJVUZPZ[LU[ÄUKPUNZVU[OL*4[HZRTPNO[YLZ\S[ MYVT[OLPUJS\ZPVUVMKPɈLYLU[HNLNYV\WZ

Additionally, we found a negative correlation between FSIQ and performance on all local-global processing measures (except the similarity cost of the VS task), indicating that a higher FSIQ is associated with better local and global processing abilities and with a more globally oriented processing style (in line with Booth, 2006).

.P]LU [OL Z[YVUN LɈLJ[Z VM IV[O HNL HUK -:08 VU SVJHSNSVIHS WYVJLZZPUNP[PZJSLHY[OH[NYV\WKPɈLYLUJLZPU[OLZL]HYPHISLZHYLWV[LU[PHS confounds that should be controlled for, either by matching the groups on these variables or by including age and FSIQ as a covariate (however, see Dennis et al., 2009, for the risks associated with controlling for IQ). Furthermore, since NYV\W KPɈLYLUJLZ PU SVJHSNSVIHS WYVJLZZPUN HYL ZVTL[PTLZ YLZ[YPJ[LK [V H particular gender or age group, it is important to investigate these abilities in males and females and across a wide age range to obtain a full picture of local-global processing in individuals with ASD.

4.3. Correlations among local-global measures

To examine whether local and global processing abilities are in direct [YHKLVɈ VY JVUZ[P[\[L PUKLWLUKLU[ HIPSP[PLZ ^L JHSJ\SH[LK [OL T\[\HS JVYYLSH[PVUZIL[^LLU[OLSVJHSNSVIHSTLHZ\YLZ0M[OL`HYLPUKPYLJ[[YHKLVɈ a negative correlation was to be expected, whereas no correlation was expected between independent abilities.

128 Local-global visual processing in ASD

Zero-order correlations between the local-global measures indicated a strong positive correlation between all measures. However, as mentioned above (see section 4.2), all local-global measures were also highly correlated with age and FSIQ. After controlling for these potential confounds, only one weak correlation remained between the local-global processing measures: We found that faster target detection on the VS task, thought to measure local WYVJLZZPUNHIPSP[PLZ^HZHZZVJPH[LK^P[OPUJYLHZLK*4ZLUZP[P]P[`YLÅLJ[PUN low-level global processing skills. Such a positive association was not anticipated, as it indicates that local and global processing abilities are not in [YHKLVɈUVYPUKLWLUKLU[I\[WHY[PHSS`[HYNL[[OLZHTL\UKLYS`PUNJVUZ[Y\J[ This association might depend on a common ‘general visual processing ability’. Yet, it might also maintain that the VS task additionally requires low- level integration of information, as argued previously (see section 4.1.2), and [O\ZUV[VUS`YLSPLZVUSVJHSWYVJLZZPUNHIPSP[PLZ6\YÄUKPUNZWHY[PHSS`TH[JO with previous observations of Booth (2006). Based on a factor analysis of low-level visuo-spatial tasks measuring local-global processing she obtained two factors: a visual segmentation and a visual integration factor. Both MHJ[VYZ^LYLWVZP[P]LS`JVYYLSH[LKPU[OL;+ZHTWSLZPTPSHY[VV\YÄUKPUNZ but were negatively correlated in the ASD group. Our data, however, did not ZOV^ H KPɈLYLU[PHS JVYYLSH[PVU PU IV[O NYV\WZ 0U[LYLZ[PUNS` UV JVYYLSH[PVU was found between the VS similarity cost and any of the global processing measures, suggesting that this measure might be more independent of global WYVJLZZPUNHUKTH`IL[[LYYLÅLJ[SVJHSWYVJLZZPUNHIPSP[PLZ

-\Y[OLYTVYL UV HZZVJPH[PVU ^HZ MV\UK IL[^LLU [OL KPɈLYLU[ NSVIHS processing measures (CM and FOO task). Although both tasks require integration of visual information, the lacking correlation indicates that they THPUS`YLS`VUKPɈLYLU[WYVJLZZLZ0UKLLKHWHY[MYVT[OLMHJ[[OH[IV[O[HZRZ [HYNL[NSVIHSWYVJLZZPUNH[HKPɈLYLU[SL]LSSV^LY]ZOPNOLYSL]LSTHU`V[OLY discrepancies are present. The CM task requires integration of motion stimuli in order to segregate the coherently moving dots from the random noise. This relies on dorsal visual stream functioning, critically involving V5/MT (Braddick et al., 2003; Britten, Shalden, Newsome, & Movshon, 1992). On the contrary, the FOO task requires form or contour integration, matching this form percept with object representations stored in memory and semantically labelling them. This relies more on ventral visual stream processing and addresses brain regions up to the prefrontal cortex (Bar, 2003; Mishkin, Ungerleider, & Macko, 1983; but see Braddick, O’Brian, Wattam-Bell, Atkinson, & Turner, 2000). Other studies also found that global processing measures share relatively little variance (Booth, 2006; Milne & Szczerbinski, 2009), indicating that multiple processes are involved in perceptual integration, and suggesting [OH[KPɈLYLU[[`WLZVMNSVIHSWYVJLZZPUNJVL_PZ[[OH[TH`ILPUKLWLUKLU[VM each other. In accordance with Booth (2006), we also found no association between processing style and local or global processing abilities, implying [OL`HSZVYLS`VUKPɈLYLU[PUKLWLUKLU[TLJOHUPZTZ

Finally, increased attention to detail in daily life, as rated by the parents, was associated with reduced CM sensitivity. Daily life situations are typically

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