The Effects of a Parent-Mediated Early Toddler Intervention on Improving Language Trajectories and Joint Attention

Background:  Sensitivity and specificity for determining early risk for ASD has improved in recent years with the age of stable diagnosis rapidly approaching 18-24 months. Early diagnosis necessitates empirically based early intervention programs for infants and toddlers under two years of age. Effectiveness of early intervention for infants and toddlers is dependent on both improving child outcomes and documenting feasibility and parent acceptability. Thorough investigation of intervention models for toddlers with ASD, including analysis of language trajectories, improvements in joint attention, feasibility, and acceptability, is needed to further our knowledge of the implications of early treatment for toddlers. 

Objectives:  This study aims to investigate the effects of a brief, naturalistic, parent-mediated intervention using the motivational strategies of Pivotal Response Treatment by: 1) examining changes in toddler language trajectories, including the frequency and quality of functional communication, 2) exploring collateral gains associated with emergence of language, including joint attention, and 3) analyzing the feasibility and parent acceptability of the intervention. 

Methods:  Participants in this study were toddlers between 15-20 months who exhibited high risk for ASD, including ADOS-T classification of ASD, expert clinical judgment of ASD, and no functional language. Treatment was implemented in the home one hour per week for approximately 12 weeks. Effectiveness of the intervention was evaluated using a multiple baseline design across three participants. Weekly measures of language use were recorded including frequency, form (initiation or response), and function (request or comment, i.e. joint attention). Feasibility and acceptability were analyzed with parent fidelity of implementation and social validation questionnaires, completed anonymously by the parents. Gains in standardized measures (ADOS, Mullen, and Vineland) were also analyzed.

Results:  All toddlers were minimally verbal prior to the start of intervention and demonstrated low levels of functional communication in naturalistic interactions, resulting in a mean frequency of communication (MFC) of 2.2 (SD=2.7) across baseline. Upon implementation of the intervention toddlers demonstrated dramatic gains in verbal communication (MFC=41.7, SD=16.7), including increases in frequency of both initiations (M=20, SD=9) and responses (M=21.6, SD=9.1). Analysis of language trajectories indicated that participants initially communicated in order to request (the primary target of the intervention) and gradually began to initiate joint attention, in the form of commenting. Results of the fidelity of implementation measures and parent satisfaction questionnaires indicated satisfactory feasibility and acceptability across all participants. Finally, standardized assessments support observed findings as all toddlers improved in measures of language, socialization, and autism severity.

Conclusions:  These results suggest that a language-based PRT intervention model for 15-20-month-old toddlers at-risk for ASD has significant implications for improving developmental trajectories. Following intervention, toddlers exhibited rapid increases in the quantity and quality of functional verbal communication. The consequential development of verbal initiations, including initiation of joint attention, suggests that the intervention was effective in improving overall social motivation. Furthermore, all toddlers made notable gains in standardized measures of language, socialization, and autism severity. This treatment proved both feasible and acceptable as all parents met fidelity of implementation, found the intervention easy to implement, and reported to enjoy the intervention.