For decades, philosophers and psychologists have assumed that children understand other people’s behavior on the basis of Belief Reasoning (BR) at latest by age 5 when they pass the false belief task. Furthermore, children’s use of BR in the true belief task has been regarded as being ontogenetically prior. Recent findings from developmental studies challenge this view and indicate that 4- to 5-year-old children make use of a reasoning strategy, which is cognitively less demanding than BR and called perceptual access reasoning (PAR), in true belief tasks. I appeal to research on fluency to explain these findings. On my account, 4- to 5- year-old children understand other people’s behavior by means of BR if they experience cognitive strain (such as in false belief tasks) but they revert to simpler heuristics PAR when such an experience is missing (such as in true belief tasks).