 Philosophical and psychological theories have sought to explain both the performance of pretense and the recognition of pretense, especially concerning evidence from developmental psychology (see Lillard 2001 for an early overview). On the performance side, children on a standard developmental trajectory exhibit early indicators of pretend play around 15 months; engage in explicit prop-oriented play by 24 months; and engage in sophisticated joint pretend play with props by 36 months (Harris 2000; Perner, Baker, &amp; Hutton 1994; Piaget 1945 [1951]). On the recognition side, children on a standard developmental trajectory distinguish pretense and reality via instinctual behavioral cues around 15–18 months; and start to do so via conventional behavioral cues from 36 months on (Friedman et al. 2010; Lillard &amp; Witherington 2004; Onishi &amp; Baillargeon 2005; Onishi, Baillargeon, &amp; Leslie 2007; Richert and Lillard 2004).