Research in Developmental Disabilities 30 (2009) 1468–1480
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Research in Developmental Disabilities
A comparison of patterns of sensory processing in children with and without developmental disabilities Phoebe P.P. Cheung a,*, Andrew M.H. Siu b a
Department of Occupational Therapy, Queen Mary Hospital, Block J, Room 539, Child & Adolescent Psychiatric Unit, Hong Kong Special Administrative Region, China Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong Special Administrative Region, China
b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 7 July 2009 Accepted 10 July 2009
This study compared the patterns of sensory processing among children with autism spectrum disorder (ASD), attention deficit and hyperactivity disorder (ADHD), and children without disabilities. Parents reported on the frequency of sensory processing issues by completing the Chinese Sensory Profile (CSP). Children with disabilities (ASD or ADHD) exhibited significantly more sensory processing issues than children without disabilities. The results of GLM and discriminant analyses showed that the CSP effectively differentiated between children with and without developmental disabilities. But it failed to identify major differences in sensory processing issues between children with either ASD or ADHD. Sensory processing issues could be one of many criteria that characterize and differentiate the features of children with different developmental disabilities. Although no significant gender differences in sensory processing issues appeared, age was a significant cofounding factor in evaluating sensory processing. Children without disabilities showed some small decreases in sensory processing issues as they aged from 6 to 12 years old. Children with ASD showed some decrease in sensory processing issues over the span of their childhood, while children with ADHD showed a significant increase in auditory processing issues as well as small increases in many aspects of sensory processing. ß 2009 Elsevier Ltd. All rights reserved.
Keywords: Sensory integration Autism Autism spectrum disorders (ASD) Attention deficit hyperactivity disorder (ADHD) Sensory processing Assessment tool
* Corresponding author. Tel.: +852 2855 3105. E-mail address:
[email protected] (Phoebe P.P. Cheung). 0891-4222/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2009.07.009
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1. Introduction Sensory integration is postulated to be a neurological function that processes and organizes sensation from one’s own body and the environment. Sensory integration is the processing of sensory modality inputs from multiple sources for functional outputs that enables an individual to use the body effectively within the environment (Macaluso & Driver, 2005). Inputs from different sensory organs are thought to be processed in specialized areas in the brain; the communication within and among these specialized areas is known as functional integration. Sensory integrative function is a key aspect of clinical evaluation in assessing children with developmental disabilities, especially for children with attention deficit hyperactivity disorder (ADHD) or autism spectrum disorders (ASD). The results of the assessment are critical in planning and implementing effective intervention for the individual child. Estimated rates of sensory processing dysfunction for children with various disabilities have ranged as high as 40–88% (Ahn, Miller, Milberger, & McIntosh, 2004; Talay-Ongan & Wood, 2000). The prevalence and types of sensory processing impairments in children with ASD and ADHD are well documented in the literature (Dunn & Bennett, 2002; Rogers, Hepburn, & Wehner, 2003; Tomchek & Dunn, 2007; Yochman, Parush, & Ornoy, 2004). Review of the clinical and autobiographical literature suggests that sensory processing dysfunction in autism is global in nature and affects all the main modalities across multisensory processing systems (Kern et al., 2007; Marcus & Stone, 1993; Nelson, 1984). Estimates of sensory-perceptual abnormalities in children with autism have ranged between 42% and 88% (Baranek, 1999; Dawson & Watling, 2000), including overresponsivity to tactile input (Grandin & Scariano, 1986), auditory hypersensitivity (Williams, 1994), and attention and arousal impairments as related to the faulty modulation of sensory input (Adamson, O’Hare, & Graham, 2006). In particular, a number of studies found that impairment in auditory processing is one of the most commonly reported sensory processing impairments in children with ASD (Tomchek & Dunn, 2007). But the literature has reported both auditory hypersensitivity (Williams, 1994) and auditory underresponsivity (Baranek, 1999; Osterling & Dawson, 1994). Avoidance of eye contact and inefficient use of eye gaze was used as a clinical feature in diagnosing ASD (American Psychiatric Association [APA], 2000; Cook, 1991). Several authors have explained these features as a self-regulatory mechanism that compensates for difficulties with modulating visual input. With an overresponsivity to tactile input, children with ASD are more likely to display extreme anxiety, distractibility, inflexible behaviors, repetitive verbalizations, social withdrawal, and abnormal focused attention (Baranek, Foster, & Berkson, 1997; Grandin, 1995). In the domain of taste and smell sensation, children with ASD were more likely to have oral sensory processing challenges, such as smelling or licking uneatable objects and being picky with the texture of food, in addition to olfactory hypersensitivity (Stehli, 1991). Mangeot et al. (2001) reported that children with ADHD, as compared with the typical developing sample, displayed greater abnormalities in sensory modulation on both physiological and parent-reported measures. Compared with children without disabilities, children with ADHD exhibited greater difficulties in the sensorimotor domain, including visual and tactile processing (Hern & Hynd, 1992; Schaughency, 1986). From a sensory processing perspective, children with ADHD may not be receiving and processing sensory information properly and therefore may have difficulty producing appropriate responses at both school and home and in the community (Dunn & Bennett, 2002). Neu (1997) reported that more activity, less adaptability, and lower thresholds for sensory stimuli in infancy are related to a higher rate of diagnosis of ADHD in later stages. Researchers have further identified vestibular sensory differences in children with attentional difficulties; moreover, these difficulties interfere with the children’s performance in movement and skills development (Ayres, 1979; Fisher, Murray, & Bundy, 1991). The literature supports the observations that children with ADHD have behavioral and conduct difficulties and disruptive behavior disorders, particularly oppositional deviant disorder and conduct disorder, as well as others (Downey, Stelson, Pomerlearu, & Giordani, 1997; Dunn & Bennett, 2002; Mangeot et al., 2001). The objective of this paper was to survey and compare sensory processing issues in children both with and without disabilities, and to examine whether differences in sensory processing exist among children with ASD, ADHD, and those without disabilities. The parent or major caregiver assessed the recruited participants using the Chinese Sensory Profile (CSP), a standardized questionnaire for
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measuring sensory processing issues. We conducted both analysis of variance and discriminant analyses to examine group differences, and we discuss differences in sensory processing among groups in view of theory and previous study results. 2. Method 2.1. Participants Two groups of children were recruited for this study, including a large sample of 1840 children without disabilities and 186 children with a diagnosis of either ASD or ADHD. 2.1.1. Children without disabilities The sample consisted of 1840 children without developmental disabilities aged 3–10 years. They were randomly selected from seven primary schools and kindergartens from three major geographical areas in Hong Kong. We adopted a cluster sampling method in recruiting the participants. Using the lists of kindergartens and primary schools available from the Educational Department of the Hong Kong Special Administrative Region (HKSAR) government, we utilized a random table to choose three kindergartens and three primary schools from each area district. Starting with a geographical area from each of the three officially designated districts in Hong Kong (Hong Kong Island, Kowloon, New Territories), we obtained responses from 13 schools (7 primary schools and 6 kindergartens) to the request to participate in the study. These respondents provided 1840 sensory profiles, from which 542 children were excluded from the analyses because they were either on medication or were below 3 or above 10 years of age. The remaining children were aged from 3 to 10 years (M = 7.25, SD = 2.8). The final sample consisted of 925 (50.3%) girls and 915 (49.7%) boys. 2.1.2. Children with disabilities group A convenient sample of children with ASD and ADHD were recruited from child and adolescent psychiatric units in Hong Kong. All participants had a diagnosis of either ASD or ADHD, which meets the criteria outlined by either the Childhood Autism Rating Scale (Schopler, Reichler, & Renner, 1988) or the Diagnostic and Statistical Manual of Mental Disorders (APA, 2000). The participants recruited for this group consisted of 72 children with ASD aged 2.7–11.6 years (M = 5.4, SD = 5.4) and 114 children with ADHD aged 4.8–12 years (M = 7.9 years, SD = 1.4). Convenient sampling was adopted to collect data in a child and adolescent psychiatric unit from June 2004 to March 2007. 2.2. Instrumentation The Sensory Profile is a parent-report measure of children’s responses to sensory experience that occurs in the context of daily routines (Dunn, 1999). The instrument consists of 125 items and was standardized with a sample of 1037 American children from 3 to 10 years of age. The instrument is designed to capture sensory processing behaviors that indicate overresponsiveness (low threshold) or underresponsiveness (high threshold) to sensory experience, resulting in interference with performance in daily tasks (Ayres & Maillouix, 1981). Ermer and Dunn (1998) demonstrated that the Sensory Profile could effectively discriminate children with ASD (n = 38) or ADHD (n = 61) from children without disabilities (n = 1075). The Sensory Profile was later translated into various languages and tested for its usefulness in its cultural background (Chow, 2005; Neuman, Greenberg, Labovitz, & Suzuki, 2004; Satiansukpong, 2002; Tseng, Lin, & Hsiao, 2000). The Chinese Sensory Profile (CSP) was adapted from the Sensory Profile and reduced to 100 items to try to include clearer and more culturally relevant items (Tseng, 1998). The scale is scored on six sensory systems and two behavioral category subscales: (a) auditory processing (8 items), (b) visual processing (14 items), (c) taste/smell processing (6 items), (d) body position (8 items), (e) movement (17 items), (f) touch processing (22 items), (g) activity level (5 items), and (h) social/emotional responses (20 items). The CSP was standardized on 726 children in Taiwan. Internal consistency of the sections within the CSP ranged from .75 to .93. Interrater reliability (1–4 weeks) was equal to .597, and test–retest reliability on 45 children (2 weeks) was .93.
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Parents of the children filled in the CSP on each behavioral statement using a 5-point Likert scale ranging from 1 (always or 100%) to 5 (never or 0%). Scores lower than 2 standard deviations below the mean indicate a definite problem in sensory processing (Dunn, 1999), while scores at or above 2 standard deviations below the mean but lower than 1.5 standard deviations below the mean indicate a likely problem. 2.3. Procedure The study obtained ethical approval by the Ethical Committee of the Hong Kong West Cluster, Hospital Authority. In recruiting for and implementing the study for children without disabilities, we first obtained verbal consent from the school principal or related staff and sent a research study package to the school. The package included an introduction letter about the study that invited the school to participate, a sample letter explaining the study to parents along with a subject demographic questionnaire, and the CSP. Some schools declined the invitation to participate because of a busy schedule or a lack of staff to coordinate the testing. Parents completed the questionnaire (including the demographic questionnaire and the CSP) and returned it to the schools for collection by the researcher. Upon collecting the questionnaires, we screened out those completed by parents who had a child with a diagnosis of developmental disabilities, including ASD, ADHD, and developmental delay. For cases in which information was incomplete or unclear, we contacted the parents for clarification with the help of the schools. For the group of participants with either ASD or ADHD, we contacted and obtained informed consent from the parents prior to participation. The ASD or ADHD diagnosis was established by meeting the criteria established by at least one of the following: the Childhood Autism Rating Scale (Schopler et al., 1988) or the DSM-IV-TR (APA, 2000). The demographic data sheet and the CSP were filled out by parents for data analysis. 2.4. Data analysis We conducted a descriptive analysis of the data set to identify the distribution of responses on each item among the children without disabilities, the children with ASD, and the children with ADHD. We then performed a multivariate analysis of covariance (MANCOVA) to identify differences in sensory processing among those children with disabilities (ASD and ADHD) and those without, as well as between genders. Age was entered as a covariate in the analysis. We then examined differences between the non-disabled and disabled groups after controlling for the effects of gender and age (Table 1). 3. Results 3.1. Overall comparison of children with and without disabilities Using MANCOVA (with age as the covariate), we compared the eight sensory processing section scores of the CSP among the three groups of participants (Table 2). Multivariate tests indicated significant differences among the score profiles of the three groups (Wilks’s l = 19.77, p < .001). Univariate tests showed significant differences among the three groups on all eight subscales, including scores for auditory processing (F = 74.42, p < .001), visual processing (F = 68.54, p < .001), activity level (F = 120.93, p < .001), taste/smell processing (F = 19.65, p < .001), body position (F = 66.13, p < .001), movement (F = 34.05, p < .001), touch processing (F = 39.02, p < .001), and emotional and social responses (F = 86.68, p < .001). Post hoc analysis showed that the sensory processing scores (of all eight subscales) of children without disabilities were significantly higher than the groups with ASD or ADHD. But in pairwise comparisons, no significant differences in sensory processing scores appeared between the groups with either ASD or ADHD. The results also showed no overall gender difference in the three score profiles among the three groups (Wilks’s l = 1.21, p = .29); the results of univariate tests for the subscales revealed a similar picture. In examining sensory processing of the sample, we found that age was a significant covariate
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Table 1 Comparison of scores of the Chinese Sensory Profile among children with (ADHD or ASD) and without disabilities. Subscale
Group
Ma
SD
p
Power
Auditory processing
Normal ASD ADHD
4.20 3.44 3.47
.55 .64 .61
74.42
.00***
.99
Visual processing
Normal ASD ADHD
4.38 3.76 3.82
.48 .58 .60
68.54
.00***
.99
Activity level
Normal ASD ADHD
3.86 2.99 2.68
.69 .57 .58
120.93
.00***
.99
Taste/smell
Normal ASD ADHD
4.38 3.79 4.04
.52 .65 .62
19.65
.00***
.99
Body position
Normal ASD ADHD
4.27 3.70 3.54
.53 .66 .62
66.13
.00***
.99
Movement
Normal ASD ADHD
4.31 4.03 3.86
.18 .50 .50
34.05
.00***
.99
Touch processing
Normal ASD ADHD
4.39 4.03 4.00
.45 .54 .52
39.02
.00***
.99
Emotional/social responses
Normal ASD ADHD
4.13 3.32 3.33
.58 .60 .61
83.68
.00***
.99
a ***
F
Estimated marginal means are shown. The means were adjusted by taking out the effect of age (covariate) and gender. p < .001.
(Wilks’s l = 8.17, p < .001); as a covariate, it also exerted significant influence on five of the eight sensory processing subscale scores, including scores for visual processing (Wilks’s l = 1.15, p = .03), activity level (F = 17.33, p < .001), taste and smell processing (Wilks’s l = 2.69, p = .002), body position (F = 2.99, p < .001), and movement (Wilks’s l = 1.40, p = .02). 3.2. Auditory processing Among the eight items on auditory processing, significant differences appeared among the three groups for seven items (except for Item 4, ‘‘holds hands over ears to protect ears from sound.’’). Further post hoc comparison of group scores showed that the group without disabilities had significantly different scores from children with ASD or ADHD for Items 2, 3, 5, 6, 7, and 8, while no significant differences appeared between children with ASD or ADHD. For Item 4, we found no significant differences among the three groups. On the whole, children without disabilities had better auditory processing than children with disabilities, and the differences in auditory processing between children with ASD and ADHD were insignificant. 3.3. Visual processing For the 14 items on visual processing, significant differences appeared among the three groups on 12 items, whereas no differences were found in scores for the 2 remaining items (Item 1 ‘‘expresses discomfort with or avoids bright lights’’ and Item 3 ‘‘Is happy to be in the dark’’). Post hoc analysis showed that on 10 items (Items 2, 4–12), children without disabilities had significantly higher scores than those with ASD or ADHD, while no differences appeared between the two disabled groups. Children without disabilities had more eye contact than children with ADHD, who had more eye
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Table 2 Comparison of item scores of the Chinese Sensory Profile among children with ADHD, ASD, and without disabilities. Items
Auditory processing 1 Responds negatively to unexpected or loud noises 2 Is distracted or has trouble functioning if there is a lot of noise around 3 Enjoys strange noises/seeks to make noise for noise’s sake 4 Holds hands over ears to protect ears from sound 5 Can’t work with background noise 6 Doesn’t respond when name is called but you know the child’s hearing is OK 7 Talks self through tasks 8 Seems oblivious within an active environment Visual processing 1 Expresses discomfort with or avoids bright lights 2 Looks carefully or intensely at objects/people 3 Is happy to be in the dark 4 Writing is illegible 5 Has difficulty putting puzzles together 6 Hesitates going up or down curbs or steps 7 Gets lost easily 8 Is bothered by bright lights after others have adapted to the light 9 Has a hard time finding objects in competing backgrounds 10 Has trouble staying between the lines when coloring or writing 11 Covers eyes or squints to protect eyes from light 12 Watches everyone when they move around the room 13 Avoids eye contact 14 Doesn’t notice when people come into the room Activity level 1 Jumps from one activity to another so that it interferes with play 2 ‘‘On the go’’ 3 Spends most of the day in sedentary play 4 Has difficulty paying attention 5 Avoids quiet play activities Taste/smell 1 Deliberately smells objects 2 Avoids certain tastes or food smells that are typically part of children’s diet 3 Routinely smells nonfood objects 4 Will only eat certain tastes 5 Chews or licks on nonfood objects 6 Does not seem to smell strong odors Body position 1 Seeks opportunities to fall without regards to personal safety 2 Hangs on people, furniture, or objects even in familiar situations 3 Has a weak grasp 4 Poor endurance/tires easily 5 Walks on toes 6 Appears to enjoy falling 7 Moves stiffly 8 Appears lethargic
Groupa
p
Without disabilities (n = 1840)
ASD (n = 72)
ADHD (n = 114)
4.35 (.02) 3.44 (.02)
3.50 (.18) 2.44 (.20)
4.23 (.11) 2.24 (.13)
.001> .001>
4.45 4.12 4.32 4.35
3.76 3.78 3.71 3.33
3.67 3.83 3.42 3.40
(.10) (.13) (.11) (.11)
.001> .001> .035 .001>
(.02) (.03) (.02) (.02)
(.16) (.21) (.18) (.17)
4.45 (.02) 4.12 (.02)
3.60 (.17) 3.43 (.17)
3.73 (.11) 3.15 (.11)
.001> .001>
4.04 4.33 4.76 4.43 4.44 4.73 4.52 4.72
3.87 3.76 4.57 3.53 3.59 4.04 4.12 4.28
3.96 3.74 4.75 3.64 3.61 4.33 4.06 4.42
(.13) (.10) (.07) (.10) (.10) (.08) (.09) (.07)
.571 .001> .209 .001> .001> .001> .001> .001>
(.03) (.02) (.01) (.02) (.02) (.02) (.02) (.01)
(.20) (.16) (.11) (.16) (.16) (.12) (.14) (.11)
4.15 (.02)
3.45 (.19)
2.91 (.12)
.001>
4.48 (.02)
3.55 (.16)
3.32 (.10)
.001>
4.37 3.68 4.41 4.43
3.83 2.58 2.74 3.73
4.00 2.29 3.72 4.23
(.11) (.13) (.10) (.09)
.001> .001> .001> .001>
(.02) (.03) (.02) (.02)
(.18) (.21) (.16) (.15)
4.01 (.02)
3.17 (.17)
2.75 (.11)
.001>
3.58 3.84 3.96 3.91
3.16 3.52 2.41 2.76
2.37 3.55 2.27 2.34
(.13) (.11) (.11) (.12)
.001> .005 .001> .001>
(.03) (.02) (.02) (.02)
(.21) (.17) (.18) (.19)
4.18 (.02) 3.77 (.02)
3.79 (.18) 3.76 (.20)
3.74 (.11) 3.15 (.12)
.001> .001>
4.62 4.35 4.67 4.72
4.13 3.97 4.09 4.28
4.29 3.97 4.48 4.57
(.09) (.11) (.08) (.07)
.001> .001> .001> .001>
(.02) (.02) (.02) (.01)
(.14) (.17) (.14) (.12)
3.60 (.02)
3.07 (.20)
2.50 (.12)
.001>
4.38 (.02)
4.32 (.16)
3.99 (.10)
.001
4.48 4.13 4.69 3.93 4.68 4.32
3.64 3.06 4.31 3.44 3.83 3.68
4.03 2.85 4.44 3.05 4.22 3.58
.001> .001> .001> .001> .001> .001>
(.02) (.02) (.02) (.02) (.02) (.02)
(.16) (.19) (.13) (.20) (.13) (.16)
(.10) (.12) (.08) (.12) (.08) (.10)
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Table 2 (Continued ) Items
Movement 1 Becomes anxious or distressed when feet leave the ground 2 Fears falling or heights 3 Dislikes activities where head is upside down 4 Avoids climbing/jumping or avoids bumpy/uneven ground 5 Seeks all kind of movement interferes with daily routines 6 Prefers sedentary activities 7 Avoids playground equipment or moving toys 8 Rocks unconsciously 9 Seeks out all kinds of movement activities 10 Takes excessive risks during play 11 Dislikes riding in a car 12 Holds head upright, even when bending over or leaning 13 Twirls/spins self frequently throughout the day 14 Holds onto walls or banisters 15 Becomes disoriented after bending over sink or table 16 Becomes overly excitable during movement activity 17 Turns whole body to look at you Touch processing 1 Avoids getting ‘‘messy’’ 2 Expresses distress during grooming 3 Prefers long-sleeved clothing when it is warm or short sleeves when it is cold 4 Expresses discomfort at dental work or tooth brushing 5 Is sensitive to certain fabrics 6 Touches people and objects to the point of irritating others 7 Becomes irritated by shoes or socks 8 Avoids going barefoot, especially in sand or grass 9 Reacts emotionally or aggressively to touch 10 Rigid rituals in personal hygiene 11 Picky eater, especially regarding food textures 12 Withdraws from splashing water 13 Has difficulty standing in line or close to other people 14 Rubs or scratches out a spot that has been touched 15 Gags easily with food textures or food utensils in mouth 16 Displays unusual need for touching certain toys, surfaces, or textures 17 Avoids wearing shoes; loves to be barefoot 18 Mouths objects 19 Decreased awareness of pain and temperature 20 Doesn’t seem to notice when someone touches arm or back 21 Doesn’t seem to notice when face or hands are messy 22 Leaves clothing twisted on body Emotional/social responses 1 Uses inefficient ways of doing things 2 Seems to have difficulty liking self 3 Needs more protection from life than other children 4 Has trouble ‘‘growing up’’ 5 Is overly affectionate with others 6 Is sensitive to criticisms 7 Seems anxious 8 Poor frustration tolerance 9 Displays excessive emotional outbursts when unsuccessful at a task 10 Has difficulty tolerating changes in plans and expectations
Groupa
p
Without disabilities (n = 1840)
ASD (n = 72)
ADHD (n = 114)
4.48 4.04 4.30 4.34 3.99 4.10 4.54 4.23 3.86 4.23 4.61 4.43 4.57 4.53 4.76 3.97 4.40
4.18 3.87 4.26 4.14 3.58 3.54 4.16 3.88 3.49 3.68 4.73 4.12 4.40 3.98 4.53 3.50 4.09
4.24 3.94 4.37 4.31 2.80 4.10 4.66 2.93 2.83 3.25 4.69 4.23 4.05 4.13 4.65 2.75 3.75
(.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.02) (.01) (.02) (.02)
(.15) (.19) (.18) (.17) (.20) (.17) (.16) (.19) (.20) (.18) (.15) (.16) (.14) (.15) (.11) (.20) (.17)
(.10) (.13) (.12) (.11) (.13) (.11) (.10) (.12) (.13) (.12) (.10) (.10) (.09) (.10) (.07) (.13) (.11)
.011 .525 .842 .468 .001> .005 .026 .001> .001> .001> .473 .026 .001> .001> .034 .001> .001>
3.70 (.03) 4.24 (.02) 4.77 (.01)
3.44 (.23) 3.36 (.20) 4.51 (.12)
3.94 (.14) 3.79 (.12) 4.61 (.07)
.116 .001> .009
4.44 (.02) 4.46 (.02) 4.40 (.02)
4.04 (.18) 4.29 (.17) 4.17 (.18)
4.13 (.10) 4.37 (.10) 3.09 (.11)
.002 .386 .001>
4.54 4.24 4.57 4.52 3.97 4.47 4.56 4.51 4.63 4.43
(.02) (.03) (.02) (.02) (.03) (.02) (.02) (.02) (.02) (.02)
4.49 3.93 4.47 4.56 3.40 4.15 3.99 4.20 4.52 4.33
(.15) (.22) (.16) (.18) (.22) (.17) (.16) (.16) (.15) (.18)
4.34 4.17 4.09 4.40 3.60 4.29 3.88 4.22 4.42 3.77
(.09) (.13) (.09) (.12) (.13) (.10) (.09) (.09) (.09) (.11)
.069 .339 .001> .508 .001 .034 .001> .002 .059 .001>
4.37 4.31 4.55 4.68
(.02) (.02) (.02) (.02)
3.42 3.15 3.95 4.19
(.20) (.20) (.16) (.14)
3.75 3.58 3.74 4.53
(.12) (.12) (.10) (.08)
.001> .001> .001> .001>
4.23 (.02) 4.17 (.02)
3.41 (.19) 2.73 (.20)
3.34 (.11) 3.05 (.12)
.001> .001>
3.77 4.48 4.19 4.15 4.25 3.54 4.23 4.18 3.78
2.73 3.78 3.26 3.24 3.56 2.95 3.60 3.32 2.72
2.42 4.05 3.10 3.10 3.47 2.56 3.74 2.92 2.65
(.12) (.11) (.11) (.12) (.11) (.14) (.11) (.12) (.13)
.001> .001> .001> .001> .001> .001> .001> .001> .001>
3.10 (.12)
.001>
(.02) (.02) (.02) (.02) (.02) (.03) (.02) (.02) (.02)
3.96 (.02)
(.20) (.17) (.18) (.20) (.17) (.22) (.18) (.19) (.20)
3.25 (.19)
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Table 2 (Continued ) Groupa
Items
11 12 13 14 15 16 17 18 19 20
Expresses feeling like a failure Is stubborn or uncooperative Has difficulty tolerating changes in routines Has nightmares Has fears that interfere with daily routines Doesn’t express emotions Doesn’t perceive body language or facial expressions Cries easily Doesn’t have a sense of humor Has difficulty making friends
p
Without disabilities (n = 1840)
ASD (n = 72)
ADHD (n = 114)
4.34 4.01 4.19 4.33 4.49 4.29 4.33 3.80 4.05 4.37
3.92 3.20 3.62 4.25 3.99 3.30 3.07 3.33 3.04 2.59
3.65 2.74 3.54 4.02 4.31 3.59 3.53 3.01 3.39 3.36
(.02) (.02) (.02) (.02) (.02) (.02) (.02) (.03) (.02) (.02)
(.17) (.19) (.17) (.15) (.15) (.17) (.16) (.21) (.19) (.17)
(.10) (.12) (.11) (.09) (.09) (.11) (.10) (.13) (.12) (.11)
.001> .001> .001> .002 .001 .001> .001> .001> .001> .001>
contact than children with ASD (Item 13). Visual awareness (Item 14) was similar for children with ADHD and without disabilities, and both had significantly higher scores than children with ASD. 3.4. Activity level The results of comparative analysis using a general linear model (GLM) showed significant differences in the activity level subscale among the three groups. Among the five items, children without disabilities showed significant differences on three (Items 1, 4, and 5) from children with either ASD or ADHD, while the activity level scores of children with ASD or ADHD were similar for these items. For both Items 2 (overactive) and 3 (inactive), children without disabilities had similar scores to children with ASD, while children with ADHD had significantly lower scores than the other two groups. 3.5. Taste and smell processing Results of analysis using a GLM showed significant differences among the three groups for all six items on the taste and smell processing subscale. Children without disabilities had significantly higher scores on Item 3 (routinely smells nonfood objects) and Item 4 (will only eat certain tastes) than the other two groups, while the scores of children with ASD and ADHD were similar. On two items – Item 1 (deliberately smells objects) and Item 2 (avoids certain tastes or food smells that are typically part of children’s diet) – children without disabilities had much higher scores than children with either ASD or ADHD. For Item 5 (chews or licks on nonfood objects), children without disabilities and those with ADHD had significantly higher scores than children with ASD. For Item 6 (does not seem to smell strong odors), the only difference found among the three groups is that the scores of children without disabilities were significantly higher than those of children with ASD. 3.6. Body position Multivariate testing showed significant differences in scores among all three groups on the body position subscale. On six of the eight items (Items 1, 3, 4, 5, 6, and 8), children without disabilities had significantly higher scores than both children with ASD and with ADHD. For Item 2, children without disabilities had significantly higher scores than children with ADHD. For Item 7 (moves stiffly), children without disabilities had significantly higher scores than children with ADHD, who in turn had significantly higher scores than children with ASD. 3.7. Movement Significant differences appeared among the three groups in 11 of the 17 items on the movement subscale. No group differences were found on four items, including Items 2 (fears falling or heights), 3
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(dislikes activities where head is upside down), 4 (avoids climbing/jumping), and 11 (dislikes riding in a car). For two other items – Items 12 (holds head upright) and 15 (becomes disoriented after bending over sink or table) – post hoc pairwise comparisons revealed no significant differences among groups, although the omnibus F test was significant. On most other items (1, 5, 8, 9, 13, 16, and 17), children with ADHD tended to have the lowest movement scores among the three groups. On only Item 6 (prefers sedentary activities) and Item 7 (avoids playground equipment or moving toys), children with ADHD had similar scores to those without disabilities and a significantly higher score than children with ASD. 3.8. Touch processing In 8 of the 22 items on touch processing, post hoc analyses showed no pairwise differences among the three groups. These included Items 1 (avoids getting ‘‘messy’’), 3 (prefer long-sleeved clothing when it is warm or short sleeves when it is cold), 5 (sensitive to fabrics), 7 (irritated by shoes or socks), 8 (avoids going barefoot), 10 (rigid rituals in personal hygiene), 12 (withdraws from splashing water), and 15 (gags easily). Children without disabilities had significantly higher scores on 8 items when compared with children with ASD or ADHD, including Items 2 (expresses distress during grooming), 11 (picky eater), 13 (has difficulty standing in line or close to other people), 17 (hates wearing shoes), 18 (mouths objects), 19 (decreased awareness of pain and temperature), 21 (does not seem to notice when face or hands are messy), and 22 (leaves clothing twisted on body). For the remaining items (4, 6, 9, 14, and 16), the scores of children without disabilities were significantly higher than those of children with ADHD, but were similar to children with ASD. Only on Item 20 (does not seem to notice when someone touches arm or back) did we find that children with ASD had significantly lower scores than children without disabilities. No significant differences appeared among the three groups for Item 11 (picky eater, especially regarding food textures). On the whole, children without disabilities had the best touch processing scores, whereas children with ADHD had the lowest scores for most items in this subscale. On more than one third of the items, no differences appeared among the three groups. 3.9. Emotional and social responses The emotional and social subscale showed a clear difference in response between children with and without disabilities. In 14 of 20 items, including Items 1–10, 12, 13, 16, and 19, children without disabilities had significantly higher scores than either children with ASD or ADHD, while the latter two groups showed no significant differences. On two items – Item 17 (does not perceive body language or facial expressions) and Item 20 (has difficulty making friends) – children without disabilities had significantly higher scores than those with ADHD, who in turn had significantly higher scores than those with ASD. On Items 14 (has nightmares) and 18 (cries easily), children without disabilities had significantly higher scores than those with ADHD, while on Item 15, they had significantly higher scores than children with ASD. No significant differences appeared among the three groups for Item 14 and 15. 3.10. Discriminant analysis of matched triplets We conducted a discriminant analysis to examine whether we could use the eight subscales of the CSP to predict the participants’ membership in the three groups of children (without disabilities, with ASD, and with ADHD), as well as in the two groups of children with and without disabilities. In the three-group discriminant analysis, we selected 32 participants each from the ADHD, ASD, and without disabilities groups. The 32 triplets were matched on gender and age. In the matched triplets, 70.8% were males and 29.2% females. Their ages ranged from 58 to 144 months (around 5–12 years old), with a mean of 81.3 months (SD = 20.2). Two canonical discriminant functions were generated that accounted for 71.2% and 28.8% of the total variance, respectively. Both functions were significant (p < .01) and had canonical correlations of .62 and .45, respectively. The accuracy of participant classification using the discriminant functions was 65.6% for the estimation sample and 61.5% for the
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Table 3 Classification results for three-group discriminant analysis. Actual group
Estimation sample
a
Cross-validated resultsb
a b
Predicted group membership Without disabilities
ASD
ADHD
Total
Without disabilities ASD ADHD
24 (75.5) 5 (15.6) 3 (9.4)
4 (12.5) 21 (65.6) 11 (34.4)
4 (12.5) 6 (18.8) 18 (56.2)
32 32 32
Without disabilities ASD ADHD
24 (75) 5 (15.6) 4 (12.5)
4 (12.5) 19 (59.4) 12 (37.5)
4 (12.5) 8 (25) 16 (50.0)
32 32 32
65.6% of original grouped cases were correctly classified. 61.5% of original grouped cases were correctly classified.
Table 4 Classification results for two-group discriminant analysis. Actual group
Predicted group membership Without disabilities
With disabilities
Total
Estimation samplea
Without disabilities With disabilities (ASD or ADHD)
26 (81.2) 10 (15.6)
6 (18.8) 54 (84.4)
32 32
Cross-validated resultsb
Without disabilities With disabilities (ASD or ADHD)
24 (75) 14 (21.9)
8 (25) 50 (78.1)
32 32
a b
83.3% of original grouped cases were correctly classified. 77.1% of original grouped cases were correctly classified.
cross-validation sample (Table 3). In the cross-validation results, the correct classification rate was 75% for children without disabilities, 59.4% for the ASD group, and 50% for the ADHD group. The highest misclassification rate (25%) was between children with either ASD or ADHD. In the two-group discriminant analysis, we used the same data from the selected participants in the three-group analysis. The two groups with disabilities (ADHD and ASD) were now collapsed into one group (n = 64), so that the two groups included children without disabilities (n = 32) and those with disabilities (nASD = 32, nADHD = 32). The canonical discriminant function generated was significant (p < .001). The correct classification rates were 83.3% for the estimation sample and 77.1% for the validation sample. The correct classification rate was 75% for the group without disabilities and 78.1% for the group with disabilities (Table 4). We further conducted several analyses to examine gender and age effects in the matched triplets and found no significant gender differences on the eight subscales for all three groups. Most correlations between age and subscales were not significant, but different patterns of correlation were found for the three groups (Table 5). Children without disabilities showed some decrease in sensory processing issues on all subscales when age increased from 5 to 12 years (r ranges from .16 to .32). Children with ASD showed some decrease in sensory processing issues as age increased on four of the
Table 5 Correlation between age and the eight CSP subscales for the three groups (n = 96, 32, for each group). Group (n = 32 for each group)
CSP subscales Auditory
No disabilities ASD ADHD *
p < .05.
.32 .11 .44*
Visual .28 .17 .26
Activity level .26 .04 .11
Taste/ smell .27 .05 .22
Body position .20 .05 .26
Movement .22 .33 .10
Touch .16 .22 .27
Emotional/ social .23 .22 .28
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eight subscales, namely auditory processing, visual processing, movement, and touch processing. But we did find a slight increase in emotional/social issues as age increased. Children with ADHD, on the other hand, showed a significant increase in auditory processing issues (r = .44, p < .05) and some increases in sensory processing issues on six other subscales (r = .10 to .28) with an increase with age. Small decreases occurred in the activity level score (r = .11) with an increase in age.
4. Discussion Sensory processing findings on the CSP reported in this study replicate the results of a number of studies involving children with ASD (Kientz & Dunn, 1997; Rogers et al., 2003; Watling, Deitz, & White, 2001) and with ADHD (Dunn & Bennett, 2002; Ermer & Dunn, 1998). The significant differences in CSP scores between children aged 3–10 with and without disabilities provide evidence that sensory processing could be an indicator of developmental dysfunction in children. These findings also generally support the use of CSP as an effective tool in screening sensory processing issues in children. The children with ASD had significantly lower scores on all eight subscales than those without disabilities. This result is consistent with the work of Kientz and Dunn (1997), who found that 85% of the items on the Sensory Profile could differentiate children with ASD from those with normal development. In their study, children with ASD had significantly lower scores than those without disabilities on 8 of 10 factors on the Sensory Profile, namely sensory seeking, emotionally reactive, low endurance and tone, oral sensitivity, inattention and distractibility, poor registration, fine motor and perceptual skills, and other. When compared with those without disability, children with ADHD had significantly lower scores (i.e., higher frequency in behavior) on 118 of the 125 items of the Sensory Profile. These results were similar to the study by Dunn and Bennett (2002). The results of the GLM and discriminant analyses point out that the CSP does not differentiate very well between children with ASD and those with ADHD. This is evident from the results of the discriminant analysis of the matched triplets (Table 3) in which, of the 37 children who were misclassified using CSP scores, 17 (45.9%) had ASD but were classified as having ADHD, or vice versa. This implies that in clinical practice, children with ASD and ADHD may appear alike in terms of sensory processing issues. Other assessment criteria would be needed to highlight the differences in clinical features between the two groups. As in previous research (Dunn & Westman, 1997), this study also finds no meaningful gender differences on the Sensory Profile. But children without disabilities did show small decreases in sensory processing issues from mid to late childhood. These issues tended to increase in children with ADHD, while small increases in some sensory issues appeared for children with ASD. The overall picture is that children without disabilities and those with ASD will have some increase in sensory processing issues over the span of their childhood, whereas children with ADHD will tend to show a bit more increase over the years. It is notable that children with ADHD had significant increases specifically in auditory processing issues over time. The results show that the CSP could be a useful tool to screen children with disabilities. Children with ASD and ADHD had significantly more sensory processing issues compared with children without disabilities, though their profiles on these issues were quite similar. But the CSP, as a proxy instrument completed by parents or caregivers, is also able to provide only an initial screening of issues rather than an assessment of specific strengths and weaknesses in sensory processing. Although we were able to recruit a large sample of children without disabilities for the study, it is generally more challenging to obtain a large clinical sample. In addition, the diagnoses of ASD and ADHD are not often confirmed before ages 5 or 6 in Hong Kong, and so the youngest participant was 58 months olds (nearly 6 years old) in the comparative study. In the discriminant analysis, we matched the three group of participants based on gender and age to provide some safeguard against the alternative explanation that group differences in sensory processing result from differences in gender composition or age. But a sample of 32 triplets is considered small for discriminant analyses and could explain why the classification results were not as positive as in a previous study (Ermer & Dunn, 1998).
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5. Conclusion Sensory processing has a major impact on daily functioning. Children with disabilities, including children with either ASD or ADHD, exhibit significantly more sensory processing issues than children without disabilities. The CSP, as a proxy self-report instrument completed by parents or caregivers, may effectively identify sensory processing issues in children with or without disabilities. As the results of the GLM and discriminant analyses show, the CSP effectively differentiated between children with and without developmental disabilities but failed to identify major differences in sensory processing issues between children with either ASD or ADHD. Sensory processing issues may be one of many criteria that characterize and differentiate the features of children with different developmental disabilities. Although no significant gender differences appear to be involved in sensory processing issues, age is a significant covariate in evaluating sensory processing. Children without disabilities between ages 6 and 12 can be expected to have some degree of sensory processing issues over time. Similarly, children with ASD are likely to have some sensory processing issues over the span of their childhood; whereas those with ADHD will likely to experience a significant sensory processing issue in auditory processing as well as in most aspects of sensory processing over time. Acknowledgements We would like to thank the schools and kindergartens/nurseries that participated in the study. We also thank the Department Head of Psychiatry at University Psychiatric Unit, the University of Hong Kong for his approval to collect data. Furthermore, we want to thank Ms. Mary Chu, the Department Manager of Occupational therapy at Queen Mary Hospital for her continuous support in conducting the research and Macy Wong for her assistance in data entry. Special thanks to Dr. Mei Tseng for granting us permission to use the Chinese Sensory Profile. 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