INTRODUCTION
Exploring and playing with objects are integral parts of early development and infants show substantial changes in exploratory behaviors over the first few years of life (Belsky & Most, 1981; Bornstein et al., 2013). In contrast, children with developmental disabilities such as Down syndrome (DS) tend to be less engaged with objects and explore them less actively (de Campos et al., 2013; Fidler et al., 2019; Landry & Chapieski, 1989; MacTurk et al., 1985; Venuti et al., 2009). DS is one of the most common chromosomal disorders with an estimated prevalence of 1 in 700 live births (Parker et al., 2010). Atypicalities in object play in individuals with DS are evident as early as the infancy period and persist throughout the childhood period (de Campos et al., 2010; 2011; 2013; Fidler, Hepburn, et al., 2005; Fidler et al., 2014). For example, infants with DS between 4- to 6-month-old showed less successful grasping and fewer exploratory behaviors including reaching, banging, and rotating during an object exploration task compared to chronological age-matched TD infants (de Campos et al., 2010; 2013).11Although infants with DS are documented to show less active or reduced exploration of toys, recent work by Fidler et al (2019) indicates that this characterization of less active exploration may accurately reflect only a subset of infants with DS. Similarly, school-aged children with DS were observed during a 2-minute free play with random set of toys such as plastic coins, bracelet bands, and paper cups (Fidler et al., 2014). During the play session, children with DS were less likely to initiate actions on new toys (i.e., previously unexplored toys) and less likely to show novel functional actions (i.e., previously undemonstrated functional actions) compared to mental-age matched TD children and children with other development disabilities (Fidler et al., 2014). Overall, infants and children with DS show significant delays in their ability to meaningfully explore objects compared to mental-age matched TD children.