This study compared between the roles of the socio-pragmatic and data-driven aspects of caregiver input in the vocabulary development of both Typically Developing (TD) Children and children with Autism Spectrum Disorders (ASD). The role of Joint Attention (JA) and Supported Joint Engagement (SJE) episode types, as well as Follow-In (FI) Comments, in the vocabulary development of TD Children and children with ASD, was investigated. The children with ASD consisted of two groups: High-Verbal (HV) and Low-Verbal (LV) children with ASD, in order to assess the effects of the different aspects of caregiver input on different initial language levels. Overall, Initiating Joint Attention (IJA), Responding to Joint Attention (RJA), Joint Attention that is Mutually established (MJA), as well as the FI utterances that were produced during these three episode types during the first three visits, significantly predicted later receptive and expressive language scores at visit 6, while utterances produced during PA, as well as utterances that were not FIs, negatively predicted later receptive and expressive language scores at visit 6. SJE measures did not predict later vocabulary scores, as shown in previous literature. The findings suggest that in these groups of children, the socio-pragmatic aspects played a larger role with LV children with ASD, whereas it played a milder role with both HV children with ASD, as well as with the TD children. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]