I got a sample of Huggies Pull-Ups Training Pants in the mail. The insert had one (and only one) complete sentence, written in English, French, and Spanish:
"Pull-Ups with Learning Designs have patterns that fade when wet to help them learn to stay dry!"
Did you spot both problems with the sentence?
First, there's that pronoun, "them" in there--its only possible antecedents are "patterns"(which is the nearest and therefore assumed antecedent) or "pull-ups", neither of which can learn anything!
The other problem is a conceptual problem with the product. Assuming that we understand that it is the child wearing the pull-up who is doing the learning, what kid spends all day staring at their diaper so they can get the feedback that they peed from the visual cue? It seems like they'd feel it first. The person who is most likely to get the "fade when wet" feedback is the MOTHER (or father or other caretaker), who is the only one who #1) looks at the diaper all day and #2) has the memory capabilities to realize that the diaper has changed from several hours ago.
So they are parent-training pants, not child training pants.
I'd rather train the child, personally. And regular old cloth underwear does that fine--they FEEL it when they pee (because it runs down their leg).