What Matters for Theory of Mind?

At around 5 years of age, most children are able to demonstrate they understand that others' can have lasting counter-factual beliefs. For example, if 5-year-olds are told that Joey's mom moved a candy that Joey had previously placed on the counter, they can correctly state that Joey thinks the candy will remain on the counter. 3-year-olds will tend to say that Joey thinks the candy is wherever his mother had moved it, even though Joey has no way of knowing this - in other words, 3-year-olds are unable to correctly represent Joey's counterfactual belief. The capacity to respond correctly in such "false belief" tasks is sometimes called Theory of Mind.

Theory of Mind (ToM) is measured in several ways, including unexpected-location (as described in the example with Joey, above), unexpected-contents (in which a crayola crayon box may actually contain rubber bands, and children must predict what a naive observer would think is in side the box), and in unexpected-identity paradigms (in which a sponge may be painted to look like a rock, and children must predict how a naive observer would classify the object; also known as an appearance/reality task). Also, sometimes ToM is measured by deception tasks in which the child must deceive an opponent. In all cases, children must usually pass a control task in which they state that they know the true state of the object location/content/identity, before demonstrating their capacity for understanding other minds.

Wellman, Cross and Watson published a metanalysis of 178 different "false belief" tasks, involving thousands of subjects. The authors identified variables that explain over 50% of the variance in false-belief tasks (which is impressive, given all the uncontrolled differences between studies in terms of exact stimuli, the procedures, and the kinds of responses required of kids [i.e., verbal vs. nonverbal]. So, what factors are important for ToM, as measured through false-belief tasks?

1. Age. Not surprisingly, kids get better at false-belief with age (Wellman et al. report that some studies have oddly failed to find this relationship)
2. Framing the task in terms of trickery. The odds of being correct increase by 1.9 times (for children of all ages) if the task is framed in terms of deceiving an opponent, rather than merely reasoning about a protagonist's beliefs.
3. Participation. The odds of being correct increase by another 1.9 times (also for children of all ages) if the child participates in the task, for example by moving Joey's candy, or otherwise having a causal role in the task.
4. Emphasizing the protagonist's mental state. By encouraging children to state or picture the "mental state" of Joey, they are more likely to correctly answer questions about Joey's counterfactual beliefs. This does not enhance young children's false-belief performance to above-chance levels.
5. Making the target object not real or not present. More 3-year-olds are able to correctly answer where Joey will look for his candy if they are told that his mother had eaten the candy. This might be explained as simplifying the inhibitory requirements of the task, since the candy is no longer in any place except in Joey's counterfactual belief. However, this does not increase young children's performance to above-chance levels.
6. Temporal marking. More kids can correctly answer "Where will Joey look first for his candy?" than those who can correctly answer "Where will Joey look for his candy?" However, temporal marking only has an effect among older kids - this manipulation does not help the youngest children, suggesting their problems with false-belief tasks lie elsewhere.

Other factors did not seem to make a difference at any age, such as the nature of the protagonist (puppet vs. real person, etc), the type of target object (real objects vs. pictured object, etc), the type of question ("where will Joey look/say/believe the candy is?") and the type of task (location vs content vs identity). The authors also found that the youngest children are just as unlikely to ascribe a false belief to others as they are to ascribe a false belief to themselves. There are no significant differences between the accuracy of self and other judgments at any of the ages tested, although they are numerically different for all but the youngest age groups.

Many have argued that success in such tasks might be dually-determined by both competence and by performance. Competence refers to the conceptual understanding that others' can have counterfactual beliefs, whereas performance refers to the ability to correctly reason or response on the basis of that conceptual understanding. The authors suggest that their results are incompatible with several "performance" accounts of developmental change in ToM (which they refer to as "early competence" theories). Wellman et al. instead advocate the "conceptual change" hypothesis, which suggests that correct performance on false-belief tasks is driven by changes in competence rather than performance.

In their scathing response, Scholl & Leslie strongly object to this conclusion. In fact, they suggest that Wellman's "conceptual change" hypothesis makes only a single prediction, and that prediction is common to all ToM theories: that children should improve with age. And contrary to Wellman's claims that performance accounts are confounded by the manipulation-related improvements across all or some age-groups in various conditions in the meta-analysis, Scholl and Leslie suggest that these results are not incompatible with "early competence" theories of ToM. For our purposes here, their strongest reason for objection is that "early competence" theories do not require that task manipulations increase the youngest children's performance to above-chance levels simply because the manipulations might not attentuate task demands enough to reveal above-chance performance. Nor do they require, Scholl & Leslie argue, that only the performance of younger children improve as a result of task manipulations, since all children may benefit from eased task demands.

It seems possible that false-belief performance can be explained on the basis of relatively domain-general mechanisms like attention, inhibition, and memory. For example, many of the manipulations identified by Wellman et al. could be effective because they reduce the demand to inhibit the current true state of the world in counterfactual reasoning - such as making the target object not real or not present. Other manipulations could be effective because they direct attention appropriately - such as temporal marking or emphasizing the protagonist's mental state. Yet other factors may have more general affects on arousal and attention, such as participation and framing the task in terms of trickery. And then there are relatively simple memory demands - in other words, none of these manipulations are effective if kids simply cannot remember the previous state of the world. (This interaction is bidirectional - reducing inhibitory demands or redirecting attention may make the previous state of the world easier to remember).

It will be important for future research on ToM and false-belief tasks to distinguish the contributions of these processes. Of course, no task is ever completely process pure - so techniques like latent variable analysis are likely to be very important in determining whether ToM performance can be predicted on the basis of these domain-general mechanisms, or whether ToM performance seems to rely on a more unique or specific skill.

10/19/2006: I made a few edits to clarify that ToM is not the same as false-belief performance, but that false-belief performance is just one process-impure way of measuring ToM.