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pneApparently, the allomorph [Iz] of the English plural morpheme is the last for children to acquire (though I'm not sure whether [s] - as in "cats" - or [z] - as in "dogs" - tends to come first).
At any rate, Amy seems to have all three now... she pointed at a picture in her book and said that the birds on that page were "gooses".
Yay for allomorph acquisition! Though, unfortunately, no points for you in this particular word :)
