Joint Attention Skills Concurrently Predict Receptive Vocabulary in Minimally and Low Verbal Youth with ASD

Background: While 30% of individuals with ASD are classified as minimally or low verbal, little is known about the correlates of language ability in this population (Tager-Flusberg & Kasari, 2013). It has been argued that joint attention (JA) skills, which are often impaired in ASD (Mundy, Sigman, Ungerer, & Sherman, 1986), are a precursor to language development (Tager-Flusberg, Paul, & Lord, 2005). However, several studies that have found a relation between language and JA skills in ASD have not differentiated between responding and initiating JA (e.g., Bean & Egisti, 2012). Furthermore, many of these studies have been conducted with young and/or verbally fluent samples (e.g., Dawson et al., 2004). Thus, there is a need to explore the relation between specific types of JA skills and language in older, minimally and low verbal youth with ASD.

Objectives: To investigate the relation between joint attention (JA) skills and concurrent receptive vocabulary in minimally and low verbal youth with ASD.

Methods: 59 minimally and low verbal youth with ASD (41M, 18F), ages 5.33 to 20.92 years, participated in this study (Table 1). Raw scores from the Initiating Joint Attention (IJA), Responding Joint Attention (RJA), Pointing, and Showing items of the Autism Diagnostic Observation Schedule-2 (ADOS-2; Lord et al., 2012) or the Adapted ADOS (A-ADOS; Hus & Lord, in preparation) were collected. Youth also completed the Peabody Picture Vocabulary Test-4 (PPVT-4; Dunn & Dunn, 2007), a standardized measure of receptive vocabulary. Non-verbal IQ (NVIQ) was measured using the Leiter International Performance Scale-3 (Roid, Miller, Pomplun, & Koch, 2013).

Results: Age was not significantly correlated with JA or PPVT-4 scores (ps > .1). NVIQ however was significantly correlated with RJA and PPVT-4 scores (r_s=-.273, p=.037; r_s=.364, p=.005, respectively). When controlling for age, NVIQ, and gender, RJA, Pointing, and Showing scores were significantly correlated with PPVT-4 scores (r_s=-.278, p=.038; r_s=-.315, p=.018; r_s=-.337, p=.01, respectively), while IJA scores were not significantly correlated with PPVT-4 scores (r_s=-.212, p=.116) (Figure 1).

Conclusions: The findings demonstrate that better RJA, Pointing, and Showing, but not IJA, skills are related to higher receptive vocabulary in minimally and low verbal youth with ASD. The results may be explained by the scoring guidelines for these ADOS items. The RJA item includes response to both gaze and gesture (i.e. pointing and showing), while the IJA item includes initiation of gaze only. Importantly, the Pointing and Showing items include initiation of these gestures. Therefore, deficits in JA skills, particularly the response to and initiation of explicit pointing and showing gestures, may explain why some youth with ASD fail to acquire receptive language. Gaze may have less of an influence on acquisition of receptive language in these older youth with ASD. Future studies should examine the relation between language and objective measures of gesture versus gaze skill. The findings also highlight the importance of targeting non-verbal communication skills, particularly explicit gesture behaviors, in interventions to improve language outcomes throughout development.