Table 2.

Descriptions of clinical neuropsychological cognitive flexibility tasks, involved neural networks (see for other external validity measures Willcutt [57]), number of included studies and participants and the effect size (Cohen’s d)

Task	Description	Main dependent measures	Potentially involved neural networks [59–65]	Number of studies	Total N	Range effect size (pooled effect sizee)
WCST	A sorting task that requires participants to determine how to sort cards on the basis of unknown categories (color, form and number). The participants need to infer the sorting rule based on the given feedback. Without notice to the participant, the sorting rule changes following a met criterion and the participant must inhibit (i.e. suppress) the previous sorting rule and subsequently discover the new sorting rule.	Number or % pers answers Number or % pers errors Number of categories	Left and right inferior frontal and DLPFC, parietal cortex, premotor area, ACC and cerebellum	12	ASD=520 TYP=479	0.25–1.01 (0.64)
MCST	Similar to WCST, but with less cards and a warning is given when sorting rule changes.	Number of errors	No studies available	2	ASD=42 TYP=45	0.05 (for only 1 study data reported)
CANTAB®a ID/ED	Shifting task that requires rule acquisition and reversal. The sorting rule can change within one dimension (ID shift) or across different dimensions (ED shift). For details see Box 1 and Figure 1 in main text.	Number of trials to criterion Number of errors to criterion	ID: orbito frontal cortex (OFC) and striatal functioning ED: DLPFC and OFC	6	ASD=184 TYP=180	0.02–1.00 (0.35)
TMTb	Timed task that requires the participant to connect a series of letters and numbers in ascending order while alternating between numbers and letters (second part, B). In the first part (A) only numbers need to be connected and no letters are presented.	Time B–Time A Ratio Time B: Time A	DLPFC, supplemental motor areas and dorsal ACC	5	ASD=281 TYP=246	0.5–1.32 (0.89)
D-KEFSc-TMT	This task consists of five conditions that assess visual-motor sequencing, visual scanning, number-letter switching and motor speed. The number-letter switching task requires participants to alternate between connecting numbers and letters.	Time switch condition	Lateral PFC	1	ASD=17 TYP=17	0.56
BADSd Rule shift Cards	To test the ability to shift from one rule to another (first rule is to respond to the color of the shown card and the second rule is to respond to the color of the previous card in comparison to the current card) and to keep track of the color of the previous card and the current rule.	Number of errors	No studies available	1	ASD=22 TYP=22	0.64
D-KEFS Color-Word	A Stroop like task with a fourth condition in which the interference condition is repeated, only now half of the stimulus words are encased in a box. The participant names the dissonant ink color except for the boxed words, in which case the participant must switch sets and read the word itself (and not name the dissonant ink color). Hence, the participants need to switch between four different rules.	Time switch condition Number of errors switch condition	No studies available	2	ASD=35 TYP=35	0.52–1.30 (0.92)

Note: the task-switching paradigm is described in the main text.

^aCANTAB^®, Cambridge Neuropsychological Test Automated Battery.

^bChildren’s version is called the children’s color trail test (CCTT) and uses colors and numbers instead of letters and numbers.

^cD-KEFS, Dellis-Kaplan executive function system.

^dBADS, behavioral assessment of the dysexecutive syndrome.

^eThe studies often differed in the reported dependent measures. This implies that for most tasks a pooled effect was calculated across different measures. This means that the pooled effect size needs to be interpreted with caution. In calculating the pooled effect size, we incorporated the number of participants for each of the effect sizes like Wilcutt [57]. The reported effect sizes are potentially biased because some studies partly included the same participants. Hence, the same participants are sometimes included twice (see Table S1 in supplementary material). Please note that we could not calculate the pooled effect size for the task-switching paradigms as the paradigms were very different from each other and not all studies reported the mean scores and standard deviations. The number of participants in the four task-switch studies was 66 ASD and 71 TYP.