For parents to provide effective support for their children's language development, they must be attuned to their child's changing abilities. This study presents a theoretically driven strategy that addresses a methodological challenge present when tracking longitudinally the cessation or "fading" of behaviors by capturing withdrawal of maternal assistance over time relative to change in child participation. Data are the co-constructed narratives of 31 mother-child dyads when the children were 3, 4, and 5 years old. Responsibility for providing narrative macrostructure shifted from children relying on maternal prompts to contributing them spontaneously, while maternal contributions showed a gradual cessation. The findings support the notion of bidirectionality in co-construction and are interpreted using a dose-effect model of the shift in responsibility for the narration over time with implications for intervention.