Yes, nice example. In the second sentence we unthinkingly fill in the missing clause "when you are with a pet". I bet adults do that all over the place. —Dan ----- The example I like of how we use world-knowledge to resolve ambiguities so easily that we don't even notice the existence of the ambiguity is the pair of sentences "Safety glasses must be worn when in the laboratory" and "Pets must be carried when on the escalator" These are grammatically parallel, but if you're in the lab without glasses, you need to go get some. But if you're on the escalator without a pet, you don't need to go get one. -----