 This approach to understanding how we attribute mental states to others has several notable features: (i) it dovetails with the dominant approach to solving the knowledge-of-other-minds problem as it proposes that our belief here is the result of postulating mental states as the best explanation of observed behavior; (ii) it dovetails with a functionalist account of mind; and (iii) it can solve the asymmetry problem, as some hold the child comes to attribute mental states to herself on the same model as she does others (Gopnik 2009). All three features of this theory have come under criticism. This approach has also been challenged by further empirical work that purports to show that infants as young as 15 months have the concept of false belief (Onishi &amp; Baillargeon 2005). One suggestion to accommodate this data is that we postulate two systems: one that operates in the infant and that is fast, efficient, inflexible and non-normative, and another that develops later (and operates in tandem with the earlier one in the mature human) and that is effortful, inflexible, normative and language-dependent (Apperly and Butterfill 2009; for a good summary of this work and a critique of it, see Jacob forthcoming).