Many aspects of human behavior are the result of internal mental states such as beliefs and desires. Furthermore, as is well known, even young children perceive, interpret, predict, and explain the behavior of others in terms of their underlying mental states. The acquisition of such abilities collectively referred to as a “theory of mind” is early, universal, seemingly effortless, and largely dissociable from more general intellectual development. In adults, the exercise of such abilities is often irresistible and seemingly instantaneous.

One hallmark of a mature theory of mind is the ability to reason about false beliefs: One can often successfully reason about true beliefs simply by considering the world itself as a proxy, but this heuristic fails in the case of false beliefs. As such, successful reasoning about false beliefs is a sufficient criterion for the existence of a theory of mind. It is precisely this ability that is tapped by the “false-belief task,” wherein a child must infer that a protagonist will look for a target object where he mistakenly believes it to be, rather than looking at its actual location.

Of course, solving a false-belief problem also requires several other abilities that are not theory of mind specific, and the existence of theory of mind in young children is also indicated by many other types of experiments. Still, given the degree to which this single task has dominated developmental research on the theory of mind, the meta-analysis conducted by Wellman and colleagues (2001) is extremely welcome.

Furthermore, we agree that this analysis is methodologically useful: for example, it identifies several factors that, thus far, appear to play no substantive role in false-belief performance; it might be more permissible for future studies to ignore such variables (but see our final comment later). Aside from these methodological morals, however, this analysis, with one exception, does not lead to any theoretical progress concerning the nature of the mechanisms that underlie the existence and development of the theory of mind.

The one exception is that the meta-analysis confirms an important role for “executive processes” in false-belief performance, a finding that should encourage the “early competence” theorist. In any case, the results of this meta-analysis are perfectly compatible with early competence accounts that posit a specific, innate, and possibly modular basis for a theory of mind.