Sensory and Motor Behaviors of Infant Siblings of Children With and Without Autism

Method

Results

The study sample included 8 girls and 5 boys in the high-risk group (mean age 12.6 mo) and 7 girls and 5 boys in the low-risk group (mean age 12.1 mo). Most participants were White, and all were from New England. The groups did not significantly differ with respect to race, gender, and age. Follow-up at age 30 mo indicated that four of the high-risk infants met criteria for ASD, and another two children had received early intervention services for mild developmental concerns. None of the children received early intervention services before 12 mo of age, and none of the infants placed in the low-risk group exhibited developmental concerns.

The developmental profile of the high-risk group fell largely within the low end of the average range, although some relative strengths and weaknesses are noteworthy. A summary of these results is presented in Table 1. Fine motor performance and visual reception skills fell in the average to above-average range, whereas gross motor skills were within the low-average range. Test scores measuring social and communication skills were mixed, although most fell within the low-average to below-average range. The number of markers noted using the AOSI indicated that 31% of the children were at high risk for developing ASD. Sensory processing differences were also found; scores from the high-risk group reflected less sensory-seeking behavior than scores of children from the normative sample and a tendency for more difficulties in the area of auditory processing.

The results of the one-sample t tests revealed some significant differences between the scores of this group and the normative data for each of the tests. On the Mullen Scales of Early Learning, scores from the high-risk group were higher on Visual Reception (t [12] = 2.1, p = .059), approaching significance, and significantly higher on the Fine Motor Scale (t [12] = 3.2, p = .009). Performance of the high-risk group was, however, significantly poorer on the Expressive Language (t [12] = −3.6, p = .004) and Receptive Language (t [12] = −3.7, p = .004) scales. On the VABS, the Motor Scale showed significantly lower scores for the high-risk group than the normative sample (t [12] = −2.4, p = .03); there were no other significant differences.

Videotaped coding of sensory and motor behaviors during play and feeding revealed that compared with infants from the low-risk group, the high-risk group demonstrated significantly fewer movement transitions (t [23]= −2.4, p = .03) and less object manipulation (t [23] = −2.4, p = .03; see Table 2). Thus, children in the high-risk group tended to move around less during the play session, and they manipulated objects in their hands less frequently (see definitions in the Appendix). No significant differences were found between groups on the other sensory and motor behaviors coded during the play sessions, and no differences between groups were noted on the behaviors coded from the feeding sessions.

Discussion

The results suggest that contextual, play-based observations in conjunction with standardized developmental measures may have a vital role in the early detection of ASD. In this study, how the infants used their hands to manipulate toys in play and how much they moved around during play appeared to be important considerations. Although many of the high-risk infants scored within the normal range on the standardized motor measures, during more unstructured play, they used less sophisticated functional fine and gross motor movements than would be expected.

An examination of the variability and frequency of the sensory and motor behaviors that were observed and coded during the play sessions provides some insight into which behaviors may be useful for future consideration related to screening for ASD. For example, behaviors that were coded as being absent or not observed in almost all intervals would not be helpful, such as movement stereotypy; aversive responses to visual, auditory, and tactile sensory input in both feeding and play sessions; construction play; and motor imitation during feeding. Behaviors that were seen a moderate amount of time that appear more promising as possible early markers in young infants include object stereotypy; mouthing of objects; motor imitation during play; and spontaneous sensorimotor, functional, and associative forms of play.

It was somewhat surprising to find no differences between groups in the frequency of functional, sensorimotor, and associative forms of play. It may be that differences in types of play and other behaviors may not be clear until after age 12 mo. Christensen et al. (2010), for example, in a study of infant siblings of children with ASD at age 14 mo, found that high-risk infants engaged less often in functional play than did age-matched, typically developing counterparts.

During the feeding session, the finding of no significant differences in sensory or motor behaviors between groups may be explained in part by the nature of the context. First, the opportunity for movement was limited in the high chair to largely oral–motor and upper-extremity movement. Second, the task of feeding is familiar and routine and lends itself to little variation in how it is performed. It may be that such a familiar task, with little variation in how it was carried out among the dyads, resulted in similar sensory and motor behavioral responses from the infants.

The developmental profile of the high-risk group in this study was consistent with that found in other studies of young siblings, which have found relative strengths in visual–perceptual skills, motor performance falling within the low end of the average range or borderline, and difficulties in receptive and expressive language (Landa & Garrett-Mayer, 2006). We also found sensory processing differences in the high-risk infant siblings, detected through the use of the Infant–Toddler Sensory Profile (Dunn, 2002). In particular, the high-risk infants tended to be less sensory seeking, a finding consistent with that of Ben-Sasson et al. (2009). It may be that early on, these infants have less capacity or motivation for exploration within their natural environments. It may also be an adaptive response learned by the infants to avoid exposure to sensory stimulation that they may experience as distressing.

Prospective study designs have been helpful for supporting research in the design of valid screening and evaluation instruments for young children before age 2 yr. Zwaigenbaum et al. (2007) reported that valid instruments are becoming increasingly available, and clinicians trained in their use are showing evidence for reliable and stable early diagnosis (as early as age 2). Although consensus on the need for universal screening has not yet been reached, early identification of ASD provides families with important information and resources. With very early entry into effective intervention services, the possibility for significant reductions in symptoms associated with ASD, or even the possibility for prevention, is promising.

Limitations and Future Research

A number of limitations must be considered in the interpretation of this study’s findings. First, the sample size was small, which increases the risk for Type I error, and because only predominantly White families from New England were represented, generalizability is limited. Second, the high-risk group, as expected, was quite heterogeneous in that 4 children ultimately were diagnosed with ASD, 2 children received early intervention for speech and language concerns but were not diagnosed with the disorder, and 7 were not identified as having any neurodevelopmental disorder or delays in development. In addition, a few of the children who were diagnosed with an ASD may have represented a broader ASD phenotype with subtle characteristics of the disorder, but not to the extent that a diagnosis was made. Therefore, as more data are collected, analyses using data from only those children who eventually have confirmed ASD diagnoses would provide a clearer picture of early markers.

The inconsistency in scores across the measures of social and communication skills is also a weakness of the study and may be attributed in part to the specific characteristics of the tests used and the differences in the measures’ sensitivity for detecting differences in children at age 12 mo. For example, the expectation of word utterances at 12 mo of age is very low for even typically developing infants. Therefore, this type of test item is not as discriminating as it would be for children at age 18 mo. The study design would also have been strengthened if all data had been coded by researchers blind to group assignment; although we attempted to blind researchers, occasionally they were able to hear siblings on the videos in the background, and because of limited resources, only about 70% videotapes were coded blindly. Therefore, researcher bias may have affected the coding, although the operational definitions of the behaviors and strong interrater reliability data addressed the risk of researcher bias to some degree.

Ongoing research is needed to further develop and validate screening and assessment measures for early diagnosis. Larger studies that systematically collect data longitudinally from at-risk infants from more diverse populations at multiple time points, such as at 6, 12, 18, and 24 mo of age, would provide a more in-depth understanding of potential markers and increase generalizability. In addition, an analysis of data from only those children who eventually develop ASD would provide more clarity with respect to potential markers for early screening and diagnostics.

Implications for Occupational Therapy Practice

The results of this study have the following implications for clinical occupational therapy practice: