A child-centred exploration of the relevance of family and friends to theory of mind development.

Theory of Mind (ToM) is said to develop at around 4 years old. But some studies suggest it develops considerably earlier than this, with others suggesting it develops much later. Although several recent studies have found that social factors (like gender, family size, number of siblings, and number of friends) can impact on ToM, other studies contradict those findings. We wondered whether addressing several procedural issues and ensuring the task concerns real protagonists in real time, would bear on the above issues. Here, 114 children of 3-6 years completed four ToM tasks incorporating controls from experimental psychology, including randomly varying the order of ToM and non-ToM questions across participants. Now, children passed ToM tasks from around 5 years old, rather than 4 years or earlier. Girls did not develop ToM any earlier than boys. There was clear correlational evidence for the older-sibling effect and effects of friends but no reliable effects of nuclear or extended family. However, when these factors were set in the context of one another, the sibling effect was driven by a negative influence from younger siblings (as opposed to older siblings) and the friends effect was driven by friends at school (as opposed to friends at home). Finally, "friends" was a stronger predictor than siblings but memory (a cognitive factor) and age (a maturational factor) were the strongest predictors of all.