Table 6 Item-level analyses comparing SAS, AS, and autism across individual SCQ items (excluding participants under 4 years)

Reciprocal social interaction

9

Inappropriate facial expressions^b

44

19

26

27.351

< .001

SAS > AS**, aut**

10

Use of other’s body to communicate

50

45

48

3.949

.137

19

Friends

27

31

44

8.065

.018

26

Eye gaze^{c, d}

43

25

37

14.526

.001

SAS > AS**

27

Social smiling^{c, e}

44

15

40

38.013

< .001

SAS**, aut** > AS

28

Showing and directing attention^{b, c}

44

25

25

20.546

< .001

SAS > AS**, aut**

29

Offering to share^{f, g}

34

30

49

13.224

.001

aut > SAS*, AS**

30

Seeking to share enjoyment^{b, c}

46

25

34

19.229

< .001

SAS > AS**, aut*

31

Offering comfort^{f, c}

36

31

43

4.931

.088

32

Quality of social overtures^{b, c}

48

25

29

26.042

< .001

SAS > AS**, aut**

33

Range of facial expressions^{f, c}

34

19

47

27.307

< .001

SAS*, aut** > AS

36

Interest in other children^{b, g}

39

21

50

30.522

< .001

SAS**, aut** > AS

37

Response to other children’s approaches^{b, g}

41

18

47

32.785

< .001

SAS**, aut** > AS

39

Imaginative play with peers^{f, c}

7

45

54

87.752

< .001

AS**, aut** > SAS

40

Group play^{b, c}

14

38

52

48.159

< .001

aut** > AS > SAS**

Communication

2^a

Conversation

11

-

19

4.373

.061

3^a

Stereotyped utterances

11

-

39

-

.098

4^a

Inappropriate questions

6

-

26

1.813

.219

5^a

Pronoun reversal^b

9

-

35

-

.103

6^a

Neologisms

9

-

34

-

.259

20^a

Social chat^f

8

-

32

-

.080

21

Imitation^{b, c}

30

43

48

10.794

.004

aut > SAS*

22

Pointing to express interest^{f, c}

38

33

46

6.147

.047

23

Gestures^{b, c}

43

34

42

4.651

.101

24

Nodding to mean yes^{b, c}

27

37

46

10.355

.006

aut > SAS*

25

Head shaking to mean no^{b, g}

34

33

42

2.063

.359

34

Imitative social play^{b, c}

25

36

46

12.860

.002

aut > SAS**

35

Imaginative play^{b, g}

24

44

47

21.433

< .001

AS**, aut** > SAS

Restrictive, repetitive, and stereotyped behaviour

7^a

Verbal rituals

12

-

35

-

1.000

8

Compulsions and rituals^{h, c}

38

14

47

39.711

< .001

SAS > AS**, aut** > AS

11

Unusual preoccupations

26

24

43

12.247

.002

aut > AS*

12

Repetitive use of objects

33

48

42

5.659

.060

13

Circumscribed interests

34

24

40

8.557

.014

14

Unusual sensory interests

27

38

46

9.559

.009

aut > SAS*

15

Hand and finger mannerisms

34

43

52

9.351

.009

aut > SAS*

16

Complex body mannerisms^g

21

26

45

17.471

< .001

aut > SAS**, AS*

Not in algorithm

17

Self-injury

25

28

36

2.781

.250

18

Unusual attachment to objects

31

7

31

28.419

< .001

SAS**, aut** > AS

38

Attention to voice^{b, c}

42

21

45

25.447

< .001

SAS**, aut** > AS