And because of the inevitable challenge studies on sex face in persuading people to respond honestly, the findings should be treated with some skepticism.
I had to read the above passage a couple of times to figure out the proper meaning. English is a marvelous language in which words can be adjective or noun, or noun or verb, depending on context. Here a comma placed after "challenge" would have been most helpful. Yes, good grammar generally forbids a comma after an introductory prepositional phrase, but it's allowed if the phrase is long.
Ambiguous writing may be a continuation of the Wall Street Journal's subtle campaign to stretch the brains of its readers.