Considering Visual Stimuli as an Active Ingredient in Vocabulary Interventions with Children on the Autism Spectrum: Evidence from a Scoping Review

Abstract

Purpose: Children with ASD demonstrate different visual processing profiles than typically developing children (Walton & Ingersoll, 2013; DiCriscio & Troiani, 2018). Evidence suggests that children with ASD may demonstrate overselectivity (i.e. overgeneralizing labels to other objects), weak central coherence (i.e. heightened local over global focus), and difficulty inhibiting distractor information, all which negatively impact word learning. These theories, as well as other evidence, suggest that children with ASD may perform best with iconic visual stimuli, especially children with severe language impairment and severe ASD. Iconic stimuli are those that most closely represent the referent and may often include objects and color photographs, with less iconic stimuli representing the referent more loosely, including line-drawings and clip-art. Language interventions targeting word learning use visual stimuli to teach word labels. However, children’s performance with various stimuli during these interventions has not been closely explored. Therefore, this scoping review was conducted to answer the following questions (1) Does visual stimuli selection in language intervention impact outcomes in children with ASD? If so, how; (2) Does the relationship between stimuli selection and language outcomes vary by the child’s pre-treatment language skills and/or ASD severity; and (3) Does intervention mode have an effect on type of stimuli selected? Methods: A scoping review protocol was developed based on previously reported frameworks for conducting scoping reviews (Arksey & O’Malley, 2005; Peters et al., 2015). This protocol followed a 5-stage process including: (1) identifying the research question, (2) identifying relevant studies, (3) study selection, (4) charting the data, and (5) collating, summarizing and reporting the results. Relevant studies were identified through databases searches using the pre-determined search strategy. Initial searching resulted in 794 identified studies. After screening, eligibility checks and ancestral searches were complete, 18 studies were selected for inclusion in this study. To answer the study questions, each study was coded across the following parameters: (1) author(s), (2) year of publication, (3) study design, (4) # of participants, (5) participant language level, (6) participant age range, (7) ASD severity, (8) intervention type, (9) target of intervention (10) response mode of communication, (11) visual stimuli used, (12) number of words taught, (13) number of words learned, (14) number of sessions, and (15) rate of learning. Results: In the included studies, different types of visual stimuli were used, with 7 studies including line-drawings, 7 including photographs and 7 including objects. The average rate of learning was highest for those that included photographs, with the next highest for those that used line-drawings, with the lowest rate of learning from those that use objects. When split up by participant language ability, results showed that (1) children who are nonverbal had the highest rate of learning with objects (M = 1.6), (2) children who are minimally verbal had the highest rate of learning with photographs (M = 1.43), (3) children who have emerging verbal skills had the highest rate of learning with line-drawings (M =2.13). Only one study included children with average verbal abilities, which demonstrated a rate of learning of 4.17 with both line-drawings and photographs. Additionally, 11 included studies used clinician directed interventions, 7 used hybrid interventions and no studies used client-centered interventions. The hybrid interventions were all receptive, while the clinician directed interventions included both expressive and receptive labeling. Clinician directed interventions that targeted receptive labeling and used line-drawings or photographs lead to the highest average rate of learning across the studies (line-drawings M = 2.24; photographs M = 2.2). Receptive interventions had a higher rate of learning overall as compared to expressive interventions. Clinician directed interventions that targeted expressive labeling and used photographs lead to the highest rates of learning across the expressive studies (M = 1.56). Finally, interventions were sorted by technology vs. no-technology. Consistent with previous findings, interventions that included technology showed higher rates of learning than those that did not use technology. However, for those that did include technology, line-drawings (Clinician directed M = 4.17; Hybrid M = 0.81) were associated with higher rates of learning than the other stimulus types, followed by photographs and then objects. Conclusions: The results of this review demonstrate the significance of visual stimuli selection during word learning interventions, especially for children with ASD and varying degrees of language impairment. Results suggest that the visual stimulus that promotes the highest rate of learning changes as language abilities increase. Specifically, children who are nonverbal may perform best with objects, children who have minimal verbal skills may perform best with photographs and children with emerging verbal skills may perform best with line-drawings. Additionally, other interventions factors, such as use of technology and target of intervention (expressive or receptive labeling) may impact stimuli selection and rate of learning, such that interventions that include technology lead to higher rates of learning as do interventions that target receptive labeling. Other significant take-aways from this review include identification of the need for standardized reporting of visual stimuli types, child characteristics (i.e. language, ASD severity) and intervention outcomes to better allow for replication and comparison between studies. Future studies should continue investigating visual stimuli as an active ingredient during word learning interventions with children with ASD.