I've encountered an article from The Independent:
12-year-old boy who transitioned to female changes his mind just two years later
Isn't it ambiguous, how old was he at that moment? Was he 12 when he transitioned to female or when he changed his mind?
The article itself clarifies this, but I want to know is the title ambiguous for a native speaker.
It's not exactly crystal clear, but here's how I would interpret this:
[12-year-old boy who transitioned to female] [changes his mind just two years later]
A B
Part A of the headline has a past-tense verb, while Part B has a present-tense verb. Therefore, I would assume that the individual was 12 at the start of transition, and 14 when second thoughts arose.
That said, I'm just explaining my rationale for my assumptions. I'm not arguing that it's entirely unambiguous.
To reduce ambiguity, one could say:
Boy who transitioned to female at age 12 changes mind just two years later
As a footnote, I think the witty comment left by @Tᴚoɯɐuo points out something that adds to the confusion: the masculine pronoun. That's why I've deliberately omitted the possessive pronoun in my revised headline.
@choster rightly says that "the purpose of the headline is to attract readers and encourage them to read the article itself".
Even in pre-clickbait days, the purpose of a headline was primarily to entice people to read the story. Headlines are written in headlinese (and British headlinese is sometimes different in style from American, so the views of native BrE speakers are possibly more valuable here).
Features of headlinese vary but can include noun piles, omission of determiners, omission of auxiliaries, and other slightly unnatural wordings.
In headlinese, the simple present tends to stand in for the present perfect. So "France declares war" would mean "France has declared war"; "Trump announces new executive order" would mean "Trump has announced a new executive order".
Hence, "12-year-old boy who transitioned to female changes his mind just two years later" can be interpreted as "A 12-year-old boy who had transitioned to female has changed his mind just two years later". This doesn't seem to solve the problem of ambiguity, though. If anything, the literal interpretation would seem to be that he is 12 now.
For what it's worth, my assumption was that the boy was 12 when he transitioned - and this turned out to be correct. I agree with you that it seems ambiguous, but I can't say for sure whether I would have thought about the ambiguity if I had seen the headline in the wild, rather than being preconditioned by your post to see ambiguity there. If other native-speaker readers had the same interpretation as me, the question arises as to whether that's based on our parsing of the headline or whether it is just a pragmatic assumption that transitioning at the age of 10 is relatively rare and therefore less likely.
Upon reading the text the first time, I imagined the boy was 12 when he started the transition, because of the assumption that the transition should be complete and he should be a 14 year old girl now. However, based on the text itself, upon further thought, we don't know whether the transition is complete, so the text is indeed ambiguous, and can mean that he started the transition when he was 12 or when he was 10.
