Reduced forms such as the pronoun "he" provide little information about their intended meaning compared to more elaborate descriptions such as "the lead singer of Coldplay." Listeners must therefore use contextual information to recover their meaning. Across languages, there appears to be a trade-off between the informativity of a form and the prominence of its referent. For example, Italian adults generally interpret informationally empty null pronouns as in the sentence "Corre" (meaning "He/She/It runs") as referring to the most prominent referent in the discourse, and more informative overt pronouns (e.g., "lui" in "Lui corre," "He runs") as referring to less prominent referents. Although children acquiring Italian are known to experience difficulties interpreting pronouns, it is unclear how they acquire this division of pragmatic labor between null and overt subject pronouns, and how this relates to the development of their cognitive capacities. Here we show that cognitive development can account for the general interpretation patterns displayed by Italian-speaking children and adults. Using experimental studies and computational simulations in a framework modeling bounded-rational behavior, we argue that null pronoun interpretation is influenced by working memory capacity and thus appears to depend on discourse context, whereas overt pronoun interpretation is influenced by processing speed, suggesting that listeners must reason about the speaker's choices. Our results demonstrate that cognitive capacities may constrain the acquisition of linguistic forms and their meanings in various ways. The novel predictions generated by the computational simulations point out several directions for future research.