Peter Jusczyk argued that infants use prosody to parse speech into smaller units for analysis. He, along with colleagues, reported that 4.5 month old infants illustrated a preference for artificial pauses at clause boundaries in comparison to pauses at other places in a sentence; preferring pauses at clause boundaries illustrates infants' abilities to discriminate clauses in a passage. This reveals that while infants do not understand word meaning, they are in the process of learning about their native language and grammatical structure. In a separate study, Jusczyk reported that 9 month old infants preferred passages with pauses occurring between subject-noun phrases and verb phrases. These results are further evidence of infant sensitivity for syntactic boundaries. In a follow up study by LouAnn Gerken et al., researchers compared sentences such as (1) and (2). The prosodic boundaries are indicated by parentheses. In (1), there is a pause before the verb . This is also the location of the subject-verb phrase boundary. Comparably in (2), which contains a weak pronoun, speakers either do not produce a salient prosodic boundary or place the boundary after the verb