Royston, R., Oliver, C., Moss, J., Adams, D., Berg, K., Burbidge, C., Howlin, P., Nelson, L., Stinton, C. & Waite, J.

Journal of Autism and Developmental Disorders

Corresponding Author

Rachel Royston

The Cerebra Centre for Neurodevelopmental Disorders,

School of Psychology, University of Birmingham,

Edgbaston, Birmingham, B15 2TT

Email:

Telephone: 0121 414 2855

Supplementary Materials

1.  The Wessex Scales (Kushlick, Blunden & Cox, 1973)

The Wessex Scale is a 16 item informant questionnaire that assesses the social and physical abilities of individuals with intellectual disability. The measure consists of the five subscales; self-help skills, continence, literacy, speech and mobility. The Wessex has good inter-rater reliability and is argued to be an effective measure for large scale studies (Kushlick et al. 1973; Palmer & Jenkins, 1982).

Several studies utilise the self-help score of the Wessex as an estimate of degree of ability (Moss et al., 2009; Oliver, Arron, Sloneen & Hall, 2008; Richards, Oliver, Nelson & Moss, 2012). This study follows this format and utilises the self-help subscale, which has a maximum score of 9.

2.  Table 1: Subscale Reliability of the Repetitive Behaviour Questionnaire (Moss, 2006)

Subscales / Inter-rater reliability
Spearman’s
Correlation / Test-retest
Spearman’s
Correlation
Stereotyped behaviour / .68 / .87
Compulsive behaviour / .81 / .88
Restricted preferences / .87 / .66
Insistence on sameness / .70 / .86
Repetitive use of language / .78 / .71
3. Table 2. Number and percentage of individuals scoring above the clinical cut-off score on the Repetitive Behaviour Questionnaire: Item level scores and post hoc contrasts for Williams Syndrome (WS), Prader-Willi Syndrome (PWS) and Down Syndrome (DS).
Group / x2 / p value / Post hoc tests
WS
(n=90)
N (%) / PWS
(n=103)
N (%) / DS
(n=78)
N (%)
Stereotyped behaviour
Q1 Object stereotypy / 7 (8) / 14 (14) / 12 (15) / 2.57 / .276
Q2 Body stereotypy / 33 (37) / 9 (9) / 8 (10) / 29.79 / <.001* / WS>PWS, DS
Q3 Hand stereotypy / 24 (27) / 28 (27) / 16 (21) / 1.23 / .541
Compulsive behaviour
Q4 Cleaning / 11 (12) / 7 (7) / 5 (6) / 2.43 / .297
Q5 Tidying / 4 (5) / 3 (3) / 14 (18) / 15.99 / <.001* / DS> PWS
Q6 Hoarding / 22 (25) / 27 (26) / 11 (14) / 4.25 / .120
Q7 Organising objects / 10 (11) / 5 (5) / 10 (13) / 3.94 / .140
Q12 Rituals / 7 (8) / 10 (10) / 9 (12) / 0.69 / .710
Q16 Lining up objects / 6 (7) / 12 (12) / 13 (17) / 4.13 / .127
Q18 Completing behaviour / 6 (7) / 16 (16) / 15 (19) / 6.09 / .048
Q19 Spotless behaviour / 9 (10) / 13 (13) / 6 (8) / 1.18 / .554
Restricted preferences
Q8 Attachment to people / 22 (24) / 24 (23) / 14 (18) / 1.15 / .562
Q10 Attachment to objects / 12 (13) / 20 (19) / 10 (13) / 1.96 / .376
Q13 Restricted conversation / 20 (22) / 24 (23) / 10 (13) / 3.50 / .174
Insistence on sameness
Q15 Preference for routine / 32 (36) / 52 (51) / 29 (37) / 5.32 / .070
Q17 Just right behaviour / 13 (14) / 16 (16) / 23 (30) / 7.53 / .023
Repetitive use of language
Q9 Repetitive questioning / 21 (23) / 42 (41) / 14 (18) / 13.08 / .001* / PWS>DS
Q11. Repetitive phrases / 6 (7) / 14 (14) / 6 (8) / 3.11 / .211
Q14. Echolalia / 9 (10) / 14 (14) / 6 (8) / 1.69 / .430

4.  Table 3. Item-level correlations between repetitive behaviour, level of ability (FSIQ and VABS ABC score) and chronological age in adults with Williams Syndrome.

Repetitive Behaviour Item / FSIQ / VABS ABC Score / Age
Stereotyped Behaviour
Q1. Object stereotypy / -.01 / .23* / -.04
Q2. Body stereotypy / -.01 / -.09 / .07
Q3. Hand stereotypy / -.05 / -.07 / -.08
Compulsive behaviour
Q4. Cleaning / -.13 / .01 / .13
Q5. Tidying up / -.14 / -.11 / -.03
Q6. Hoarding / -.02 / -.11 / -.12
Q7. Organising objects / -.26* / -.20 / .13
Q12.Rituals / -.04 / .16 / -.10
Q16. Lining up objects / -.21 / -.22* / -.03
Q18. Completing behaviour / -.04 / -.05 / -.27*
Q19. Spotless behaviour / -.15 / -.26* / -.12
Restricted Preferences
Q8. Attachment to particular people / -.14 / -.21 / -.22*
Q10. Attachment to objects / -.06 / -.07 / -.01
Q13. Restricted conversation / -.12 / -.29** / -.15
Insistence on Sameness
Q15. Preference for routine / -.24* / -.39*** / -.05
Q17. Just right behaviour / -.18 / -.26* / -.04
Repetitive Speech
Q9. Repetitive questions / -.40*** / -.36*** / -.20
Q11. Repetitive phrases / -.14 / -.13 / -.19
Q14. Echolalia / -.19 / -.39** / -.14

*** p < .005, ** p < .01 * p <.05

5. Table 4. Mean scores and standard deviations for the total scores and five subscales of the Repetitive Behaviour Questionnaire for Williams Syndrome (WS), Prader-Willi Syndrome (PWS) and Downs Syndrome (DS).

WS
(n=90)
Mean (SD) / PWS
(n=103)
Mean (SD) / DS
(n=78)
Mean (SD)
Stereotyped behaviour / 3.04 (3.23) / 2.33 (2.85) / 1.94 (3.47)
Compulsive behaviour / 3.88 (4.79) / 4.25 (5.48) / 4.82 (6.92)
Restricted preferences / 2.98 (3.00) / 3.26 (3.43) / 2.40 (2.83)
Insistence on sameness / 2.09 (2.49) / 2.82 (2.46) / 2.67 (2.79)
Repetitive use of language / 1.97 (2.56) / 3.20 (3.58) / 1.69 (2.60)
Total score / 13.96 (11.36) / 15.86 (14.09) / 13.52  14.96)

6.  Figure 1 Further Explanation

The graphs in figure 1 depict the frequencies of repetitive behaviour. This type of graph is plotted on a scale and each item has an axis arranged radially. The axis for each item begins in the centre with the lowest value and extends towards the outside with higher values. The scale therefore displays which items are scoring high and low in frequency. For example, for the Williams syndrome group, the graph shows the frequency of hoarding is high, whereas the frequency of the other compulsive behaviours are lower, including organising objects, rituals and lining objects.

The items are organised in the graph based on the subscale they belong to. The graphs are shaded to represent which items belong to which subscale. The items and corresponding subscales are listed below:

Stereotyped behaviour; Object stereotypy, body stereotypy, hand stereotypy

Compulsive behaviour; Cleaning, tidying, hoarding, organising objects, rituals, lining up objects, completing behaviour, spotless behaviour

Restricted Preferences; Attachment to people, attachment to objects, restricted conversation

Insistence on sameness; Preference for routine, just right behaviour

Repetitive use of language; Repetitive questioning, repetitive phrases, echolalia

A + next to an item indicates that individuals with that syndrome scored significantly higher than one other syndrome group for a particular repetitive behaviour. A – indicates that the syndrome group scored lower than one other syndrome group for a behaviour. Group differences are stated parenthetically.

References

Kushlick, A., Blunden, R., & Cox, G. (1973). The Wessex Social and Physical Incapacity (SPI) Scale and the Speech, Self Help and Literacy Scale (SSL).Psychological Medicine,3, 336-378.

Moss (2006). The phenomenology of repetitive behaviour and autism spectrum disorder in Cornelia de Lange syndrome (Unpublished doctoral thesis). University of Birmingham, Birmingham, UK.

Moss, J., Oliver, C., Arron, K., Burbidge, C., & Berg, K. (2009). The prevalence and phenomenology of repetitive behavior in genetic syndromes.Journal of autism and developmental disorders,39(4), 572-588.

Oliver, C., Arron, K., Sloneem, J., & Hall, S. (2008). Behavioural phenotype of Cornelia de Lange syndrome: case–control study.The British Journal of Psychiatry,193(6), 466-470.

Palmer, J., & Jenkins, J. (1982). The ‘Wessex’ behaviour rating system for mentally handicapped people: Reliability study.The British Journal of Mental Subnormality,28(55), 88-96.

Richards, C., Oliver, C., Nelson, L., & Moss, J. (2012). Self‐injurious behaviour in individuals with autism spectrum disorder and intellectual disability.Journal of Intellectual Disability Research,56(5), 476-489.