A certain textbook, whose title and author will remain unnamed until I’ve stopped teaching from it, has the following piece of wisdom to offer on the question of whether children use certain constructions more often depending on how often these constructions are produced by adult speakers of the language.*
“Frequency certainly may have effects. For example, Gathercole (1986) found [that] Scottish children use a present perfect construction more frequently than children acquiring English; presumably Scottish adults do so also.”
For one thing, there’s no “presumably” about it – the abstract of Gathercole’s article specifically states that “Scottish adults use the present perfect construction in their speech to children much more frequently than American adults do,” and how lame is that, not to even check the abstract of the only paper you’re going to discuss under the heading of frequency effects?
More irksomely: didn’t the author realise that Scottish children are actually acquiring English?
* Sloppy wording, inconsistency in citations (some in-text, others as footnotes), obscure argumentation, unfair presentation of arguments/results which don’t fit the favoured dogma, and apparently an entire failure to find a proofreader, are some of the other unique selling points of this textbook. I hope I never have to use it again.