Eight children aged 4;1-8;1 and their primary caregivers participated in a study designed to evaluate their use of the onset cluster /str-/ in both read and conversational speech. The cluster is currently undergoing a reported sound change in many varieties of English, with the initial /s/ being retracted to [?]. The study compared the initial fricative of the cluster in both the children and their mothers. Acoustic analysis was carried out in order to categorize tokens as either [s] or [?] using spectral peak analysis. Results found that children as young as 5;1 were starting to exhibit the usage patterns of their mothers. The distribution of the novel variant suggests that the children may be learning this form via a process of lexical diffusion rather than by rule. Implications for the study of dialect acquisition and phonological acquisition in general are discussed.