The hypothesis that the acquisition order of relational words directly reflects the complexity of these words in formal linguistic analysis was tested for the singular, non-neuter person pronouns of English. Data on the development of comprehension of these pronouns gathered in two conversational situations, child as person addressed and child as onlooker, from six children (about 2 years of age) in a five-month longitudinal study indicated that the acquisition order of these words does not directly reflect linguistic complexity but rather the complexity of the percepts underlying the semantic concepts involved. Additional data indicated that children's decentering in the speech event also plays a critical role in the discrimination of the relevant semantic concepts by allowing the child to appreciate the relational nature of person pronouns. These results are interpreted as evidence against the use of formal linguistic representation as an explanation of semantic development. (Author)