I'll be giving an update on the acquisition study, PaQua.
The literature on the acquisition of the passive has generally found that (i) kids fail to comprehend all passive sentences until as late as 6 years old; and (ii) children can comprehend passives of actional verbs at an earlier age than passives of non-actional verbs, perhaps between 4 and 5 years old.
Both these observations have led to a variety of claims about children's grammatical knowledge (or lack thereof) of the passive. This study investigates the possibility that children's failure to comprehend passives of non-actional verbs in particular is due to pragmatics, not syntax.
Data is collection is ongoing, so I will be giving an update on our preliminary results.