The current study used growth curve analysis to study the role of input during the acquisition of the English causal connective "because" and its German counterpart "weil." The corpora of five German and five English children and their adult caretakers (age range 0;10-4;3) were analyzed for the amount as well as for the type of connective use--imitated, elicited, and independent. The growth curves showed that children's elicited use developed faster than their independent use; imitations were rare. Adult connective input was not found to function as a scaffold of children's connective use. Rather, the adult "why/warum"-questions played an important role in the acquisition of "because" and "weil." In turn, children also used "why/warum"-questions to elicit causal responses from their caretakers, which shows that children were responsible for a great part of their own input.