Three- and 4-year-old children were tested using videos of puppets in various versions of a theory of mind change-of-location situation, in order to answer several questions about what children are doing when they pass false belief tests. To investigate whether children were guessing or confidently choosing their answer to the test question, a condition in which children were forced to guess was also included, and measures of uncertainty were compared across conditions. To investigate whether children were using simpler strategies than an understanding of false belief to pass the test, we teased apart the seeing-knowing confound in the traditional change-of-location task. We also investigated relations between children's performance on true and false belief tests. Results indicated that children appeared to be deliberately choosing, not guessing, in the false belief tasks. Children performed just as well whether the protagonist gained information about the object visually or verbally, indicating that children were not using a simple rule based on seeing to predict the protagonist's behaviour. A true belief condition was significantly easier for children than a false belief condition as long as it was of low processing demands. Children's success rate on the different versions of the standard false belief task was influenced by factors such as processing demands of the stories and the child's verbal abilities.