This study sought to clarify the process of knowledge acquisition by examining why people tend to misattribute others' activities as their own after having interacted with them. In Study 1, an experiment was conducted with 4‐year‐old children allocated to 2 groups: one group of children interacted with an adult, and the other group interacted with a peer. The latter group was further divided into 2 subgroups on the basis of the strength of children's friendships (high intimacy vs. low intimacy). Children in the low intimacy condition demonstrated more misattributions and greater knowledge acquisition. Study 2 focused on interactions and revealed that knowledge acquisition was influenced by the nature of children's interactions, which depended on the strength of their friendships. Those in the low intimacy condition (i.e., weaker friendships) provided their peers with appropriate support sufficient to complete a task but did not unilaterally complete tasks for their peers. These results suggest that misattribution occurs when individuals actively participate in interactions with others, and that new knowledge is acquired as they internalize the knowledge of others. Highlights This paper examined the role of “error bias” (a tendency to mistakenly attribute others' activities to oneself more often than attributing one's own activities to others) in knowledge acquisition. Error bias occurred in child‐child pairs with low intimacy more often than in adult‐child pairs, as the level of intimacy leads to differences in attitudes to taking part in interactions. The findings suggest that although intimacy is useful for starting active interactions with others, meaningful interactions that lead to knowledge acquisition are developed through an individual's recognition of appropriate ways of interacting with others.