“…In early and middle childhood, there appear to be important differences in the meaning and implication of different subtypes of observed nonsocial behaviors (Coplan & Ooi, 2014). For example, whereas reticent behavior (i.e., watching other children play but not joining in, remaining unoccupied) appears to be a marker variable for shyness and anxiety (e.g., Coplan et al, 2008; Coplan, Prakash, O’Neil, & Armer, 2004; Henderson, Marshall, Fox, & Rubin, 2004), solitary-active play (i.e., repetitive sensorimotor actions, solitary dramatizing) appears to reflect social immaturity, impulsivity, and externalizing difficulties (Coplan et al, 2001; Coplan, Rubin, Fox, Calkins, & Stewart, 1994; Choo, Xu, & Haron, 2012; Evans, Nelson, & Porter, 2012; Rubin & Mills, 1988). In contrast, solitary-passive play (i.e., quiescent constructive and exploratory activities while playing alone) appears to be a comparatively benign form of nonsocial behaviors, and it has generally not been associated with indices of socio-emotional difficulties in early and middle childhood (Bar-Haim & Bart, 2006; Coplan, 2000; Coplan et al, 1994; Doctoroff, Greer, & Arnold, 2006; Lloyd & Howe, 2003; Nelson, Hart, & Evans, 2008; Rubin, 1982).…”